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How do I solve using substitute method

How do I solve using substitute method-example-1
User Ninu
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2 Answers

7 votes
choose a variable in the first equation to solve for
2x + 2y = 2
2x = 2 - 2y, divide each side by to leaving x on one side
so x = 1 - y

Now plug that in for x in the second equation
-4x + 4 y = 12
-4 (1 - y) + 4y = 12
so -4 + 4y + 4y = 12
then add 4 to each side and combine the y terms
8y = 12 + 4 = 16
8y = 16 divide both sides by 8
so y = 2


User Nikolay Osaulenko
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6.7k points
3 votes
When using the substitution method, the easiest way to start off is to make sure you have one equation set to equal either y or x. That would give you:
y=-x+1
-4x+4y=12
Then, you put the equation set to y inside the other equation to get:
-4x+4(-x+1)=12
You would the solve the equation to get:
-4x-4x+4=12
-8x+4=12
-8x=8
x=-1
Now you still have to find the y value. You would now put the x value inside either of the equations and solve it. I chose the first one and got:
2(-1)+2y=2
-2+2y=2
2y=4
y=2
Your answer is (-1,2).
User CHANTI
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6.1k points