Question 26933: how would you do substitution? i don't get it. i need it to be like broke down more like step by step. Answer by elima(1433) (Show Source): You can put this solution on YOUR website! Here's an example I'll use while I try and explain it;
2x-9y=1
x-4y=1
First you need to solve one of the equations for either x or y, we will solve the second one for x;
x-4y=1
x=1+4y
Substitute this value of x in the frist equation;
2x-9y=1
2(1+4y)-9y=1
Distribute the 2:
2+8y-9y=1
Add like terms;
2-y=1
Subtract 2 from both sides;
-y=1
You do not want to leave y negative, so you need to divide both sides by -1;
y=-1
Now that you have y, substitue that value in the second equation;
x-4y=1
x-4(-1)=1
x-4=1
x=1+4
x=5
Now you have both y and x;
x=5
y=-1
Hope this helps!
=)