Question

i need help with number 7. its solving systems of equations by substitution. please show work!!! i need help

Answer 1

-4x+y=6
-5x-y=21

Solve for one side of either equation. I will use the first equation and solve for y.

-4x+y=6
+4x +4x

Y=4x+6
-5x-y=21

Now when you substitute, make sure to distribute properly including the easily missed negative.

-5x-(4x+6)=21
-5x-4x-6=21
-9x-6=21
-9x=27
X=27/-9

X=-3


Now that you know X, substitute to find Y.

Y=4(-3)+6
Y=-12+6

Y=-6

So your final answer is:
X=-3 Y=-6
(-3,-6)