SOLUTION: 5. solve the following systems of equations x=3y+7 x+y=-5

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Question 113902: 5. solve the following systems of equations
x=3y+7
x+y=-5
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Start with the given system
x%2By=-5
x=3y%2B7



%283y%2B7%29%2By=-5 Plug in x=3y%2B7 into the first equation. In other words, replace each x with 3y%2B7. Notice we've eliminated the x variables. So we now have a simple equation with one unknown.


3y%2B7%2By=-5


4y%2B7=-5 Combine like terms on the left side


4y=-5-7Subtract 7 from both sides


4y=-12 Combine like terms on the right side


y=%28-12%29%2F%284%29 Divide both sides by 4 to isolate y



y=-3 Divide




Now that we know that y=-3, we can plug this into x=3y%2B7 to find x



x=3%28-3%29%2B7 Substitute -3 for each y


x=-2 Simplify


So our answer is x=-2 and y=-3