Question

Solve each system using elimination.

7. 4x+y=8
-3x-y=0


8. 2x+5y=20
2x-5y=3


9. 3x+2y=-10
2x-5y=3

Answer 1

7. 4x+y=8 ----- first equation
(+)
-3x-y=0
_______
x = 8 ---- second equation

substitude second equation into first equation

4(8) + y = 8
32 + y = 8
y = 24

8. 2x+5y=20 ---- first equation
(-)
2x-5y =3
________
10y = 17
y = 17/10 ---- second equation

substitude second equation into first equation

2x + 5(17/10) = 20
2x + 17/2 = 20
4x + 17 = 40
4x = 23
x = 23/4

9. 3x+2y=-10 (×2) ---- first equation
2x-5y=3 (×3)

6x + 4y = - 20
(-)
6x - 15y = 9
___________
19y = - 29
y = - 29/19 ---- second equation

substitude second equation into first equation

3x + 2(-29/19) = - 10
3x - 58/19 = - 10
3x = - 132/19
x = - 44/19