Question

Solve by elimination 8x+9y=-55 -8x+y=65

Answer 1

1. Add the 2 systems and get 10y = 10.
2. Divide both sides by 10 so you get y = 1.
3. Substitute that in either equation (I'm going to use the 2nd equation).
4. -8x + 1 = 65.
5. Subtract 1 from each side.
6. -8x = 64.
7. Divide by -8 on both sides.
8. x = -8.
9. Check in the other equation.
10. 8(-8) + 9(1) ?= -55
11. -64 + 9 ?= -55
12. -55 = -55

Answer 2

8x+9y=-55
 -8x+y=65                 (+)

10y=10  /:10

y=1

-8x+1=65

-8x=64   /:(-8)

x=-8