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Hello everyone meet again with
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Mr. Beni, hopefully you are
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all in good health there, yes, in the
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previous video, Mr. Beni has discussed the chapter on
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straight line equations, now in
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this video, Mr. Beni will start discussing the
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first part of the SPLDV chapter, namely getting to know
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SPLDV and solving it using the social
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graph method, prepare your stationery, let's
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start first, vabene will convey
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the purpose of watching this video,
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after watching this video, you
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are expected to be able to understand
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the meaning of the system of linear equations of two
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variables or later abbreviated as SPLDV,
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then determine the solution of this SPLDV
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using the graphic method Okay, let
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's just start the discussion, okay, before
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discussing more deeply about SPLDV, we
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must first understand the term
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linear equation. What is a
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linear equation? A linear equation or PL is
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an equation that only has
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variables to the power of one to
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understand better. Let's look at this table,
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the one on the left is an example of a
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linear equation and the one on the right is
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not a linear equation, you
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can see the difference. Let's pay attention
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to the linear equation, the power of
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the variable is always one, if
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the power is not written, it means
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Hi, for example, this one has x to the power of
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one, this one has x & y to the power of one too,
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here the variables used are AB and
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C has three variables all to
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the power of 1, well, these kinds of forms
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are called linear equations
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or other names are straight lines,
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so linear means a straight line, yes,
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because later if we draw it on the
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Cartesian plane, it will form a
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straight line. Meanwhile,
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the variables next to it are not cut by
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one, for example, this is to the power of two,
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this one x & y to the power of two will also be this one, there are
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even to the power of three, brother, it's
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clear, yes, which one is a linear equation, which one is
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Hi, next we also have to understand the
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term solution or completion of a
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linear equation, the solution of a
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linear equation is the values that
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can replace the variables so that
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the equation is true, to
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determine this solution, we will use the
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algebraic technique that has been studied
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in grade 7, for example, the first one is
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2 x plus 3 = 5, the solution or
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solution means the value that
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can replace the variable x so that
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this equation is True, meaning the
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point is we look for the value of x which is equal
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Hi So, the ones with ice, we collect on the
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left side, while the ones without
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ice, move to the right side, so
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if we move these three to the right, it
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becomes minus three. Then we
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simplify it. 2x = 2 means
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the unity if the ice is one it means that
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this becomes two times one plus three two times
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one yes two then plus three
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becomes 5 correct the equation then X =
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1 is the solution or solution
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of this linear equation by
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using algebraic operations you
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can also determine the solution of
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this second equation later the answer is a =
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Hi what if the form has two
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variables like this this could be the ice is 5
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it drinks one Try if we
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enter this it becomes three times 5 plus
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four times minus one this becomes 15
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minus 4 yes the result will be 11 correct
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the statement the solution is x = 5 and Y =
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minus 1 but the problem is if we
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enter another number for example x is one
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and Y2 then the result will also be 11
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if entered into this equation means
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the solution is x = 1 and Y = 2 too so
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which one is correct This one or the
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Hi so like this guys if there are two
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variables like this here the
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variables are X and Y then we need two
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equations at once to determine the
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value of X and Y which is certain if it is like
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this there is three variables means we
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need 3 equations at once so that the value of
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a b and c can also get a definite number
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Well this is what is called a
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system of linear equations for
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more details we will see on the
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next slide what is SPL a system of
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linear equations or SPL is a collection of several
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linear equations it works together
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so the key word is a collection of
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several linear equations So it's not just
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one like that If more than
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one means it's a system of
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linear equations can be understood
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Hi Well let's look at the notes first if
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there are two variables then
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two equations are needed to solve it the
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first one there is only one
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variable means just this one equation is enough
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we can know the value of the variable x
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how much will it be when that check
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yes if you enter one the answer is certain
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eh this statement becomes
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hi but if like this equation
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there are variables x and y because there are two
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variables then there must be two equations
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to determine the definite value of X and Y For
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example like this then there will
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be two equations like that Well if
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the form is two together at once
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like this then This is what is called a
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system of linear equations later
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if there are three variables like this then
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three equations are needed to
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solve it and likewise if
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four variables five variables and
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so on can be understood
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Hi now we have just entered to
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the definition of SPLDV What is SPLDV a system of
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linear equations in two variables or
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abbreviated as SPLDV is a system of
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linear equations It has two variables
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For example like this 3x + 4 y = 11 4x
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minus Y = 2 here there are two
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equations right the top and the bottom
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then there are also two variables namely
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x & y well this form is what is
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called SPLDV later then
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How to determine the value of x and y
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so like this to determine the variables in
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SPLDV means we are looking for a solution or
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solution of SPLDV in this 8th grade
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we are given four methods to
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Hi the first graphical method as the
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name suggests later we will use a
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graph to solve SPLDV then
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the second substitution method the third
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elimination method and the last
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is a mixed method between elimination
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Hi specifically for this video we discuss the
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graphical method first yes other methods will be
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discussed in the next video okay Here it is the
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graphical method as the name suggests
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later we will use a graph to
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determine the solution of an SPLDV
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the steps first draw a
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graph of each equation on the
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Cartesian plane neatly then the
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second Mark the point where the two
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lines meet now the coordinates This point
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is the solution of the SPLDV okay
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so that we understand better let's go straight to the
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first example questions Determine the solution
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of the equation x minus y = 1 and 2 X
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minus Y = 4 using the graphic method
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Hi of course we prepare the
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neat Cartesian plane first then we
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prepare to draw the graph
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we start from the equation x minus y
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= 1 to draw this graph the method is
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exactly the same as drawing the
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call graph in the previous chapter we first determine
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the point of intersection with the x axis means y
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= 0 so the equation becomes X
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minus 0 = 1 means the x is one right right
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so the coordinate will be X1
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it is zero meaning the point will be here
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continue Determine the point of intersection with the
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y axis Means x is zero so
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the equation becomes 0 minus y = 1
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minus 1 so the coordinate will be x 60 it
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is minus 1 meaning the point will be
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here now we have got two points
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just connect them so it looks like this
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Mr. Beni draw first so the
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first line equation looks like this
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now to the second equation 2x minus
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Y = 4 We first determine the point of intersection
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with the x-axis, meaning y = 0 so
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the equation becomes 2x minus 0 = 4,
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meaning x = 2, so the coordinates
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will be x-2y zero, then Determine the point of
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intersection with the y-axis, meaning x is
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Mal so the equation becomes
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meaning yeah minus time, so
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the coordinates will be x zero, it drinks
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time, meaning the point is here,
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now we have two points,
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just connect them like this,
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Hi, so the equation of the second line, well, the
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two lines meet at this point,
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the coordinates are 3.2, the solution to this SPLDV is
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x, 3y is two, finished, you can understand it, right,
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one more example so you
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understand better Determine the solution to
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the equation 2 x plus 4 y = 8 and 3x minus
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Y = minus 9 with the
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graphic method, try it yourself, okay, later
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if you have found the answer, please
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type how much x and how much Y in the
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comments column and then match it with
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the answer that Mr. Beni gave Okay, if
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so, let's discuss it, we start from the
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equation 2 x plus 4 y = 8 We
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first determine the point of intersection with the
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Oh, that means y = 0 so the equation
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becomes two x plus 4 times 0 = 8
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then this becomes 2x = 8 means x
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= 4 yes so the coordinate will be x 4y
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is zero here means the point
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Hi continue Determine the point of intersection
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with the y-axis Means x0 so
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the equation becomes two times zero
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plus 4 y = 8 then this becomes 4 y
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= 8 means Y is equal to two
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right so the coordinate will be x zero
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it is two means at this point
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Hi now we have got two points
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just connect them so the picture is
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more or less like this so the
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first equation now the
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23rd commonality x minus y = minus 9 We
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first determine the point of intersection with the
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x-axis means yes0 yes So
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the equation becomes 3x minus 0 =
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minus 9 means x = minus three yes
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so the order will be X minus three it is
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zero means it is at this point continue
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Determine the point of intersection with the y-axis
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Means x is equal to zero so
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the equation becomes three times 0
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minus y = minus 9 means y = 9 right
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so the coordinates will be x 0y 9
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Hi Well now we have got two
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points just connect them so it will be
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Hi so the equation of the second line well the
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two lines have met at
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this point the coordinates are minus 2.3 the
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solution for this SPLDV is x =
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minus 2 and Y = 3 done is there anyone Is
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the answer correct Okay like that yes it
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can be understood right Okay that's the video
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discussion about getting to know SPLDV and
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solving it with the graphical method
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for the next video Mr. Beni will
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discuss the second part which is about
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solving SPLDV with the
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substitution method so stay tuned hopefully
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this video is useful Thank you for
