SOLUTION: solve the system by substitution. 3x - 3y = -12 y = -3x - 12

Algebra ->  Graphs -> SOLUTION: solve the system by substitution. 3x - 3y = -12 y = -3x - 12      Log On


   

Question 110540: solve the system by substitution.
3x - 3y = -12
y = -3x - 12
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

Start with the given system
3x-3y=-12
y=-3x-12



3x-3%28-3x-12%29=-12 Plug in y=-3x-12 into the first equation. In other words, replace each y with -3x-12. Notice we've eliminated the y variables. So we now have a simple equation with one unknown.


3x%2B9x%2B36=-12 Distribute


12x%2B36=-12 Combine like terms on the left side


12x=-12-36Subtract 36 from both sides


12x=-48 Combine like terms on the right side


x=%28-48%29%2F%2812%29 Divide both sides by 12 to isolate x



x=-4 Divide




Now that we know that x=-4, we can plug this into y=-3x-12 to find y



y=-3%28-4%29-12 Substitute -4 for each x


y=0 Simplify


So our answer is x=-4 and y=0