Question

Solve the following by the method of your choice, and show your work:

7. x+2y=-4
-3x-2y=-4

8. 4x+y=2
y=x-3

9. 2x-3y=7
4x+y=-7

Answer 1

7. Eliminate 2y and -2y by adding —> -2x=-8 —> x=4 —> plug 4 into x in either equation —> 4+2y=-4 —> 2y=-8 y=-4
Answer: (4,-4)

8. Substitute x-3 into the y variable above —> 4x+x-3=2 —> 5x=5 —> x=1 —> plug 1 into the x variable either equation —> y=1-3 —> y=-2
Answer: (1,-2)

9. Multiply the whole top equation by 2 so 2x can become 4x and eliminate by subtracting 4x below
4x-6y=14
4x+y=-7 (SUBTRACT)
-7y=21 —> y=-3 —> plug -3 into a y variable in either equation —> 4x-3=-7 —> 4x=-4 —> x=-1
Answer: (-1,-3)

Hope this helps!