Question

Solve by the linear combination method (with or without multiplication).

4x – 5y = –18
3x + 2y = –2

A.
(3, –1)

B.
(–2, 7)

C.
(–1, 3)

D.
(–2, 2)

Is it D?

Answer 1

multiply the first equation by 2
multiply the second equation by 5

you get these two equations, which you add together:
8x – 10y = –36
15x + 10y = –10
---------------
23x + 0 = -46
23x= -46

divide both sides by 23 to get
x = -46/23 = -2

Answer 2

to find y, we can use either of the original equation. The 2nd equation has smaller numbers, so let's use that one

3x + 2y = –2
replace x with -2:
3*-2 + 2y = -2
-6 + 2y = -2
add +6 to both sides

-6+6 + 2y = 6-2
2y = 4
y=2

so (-2,2) is the answer.

we can check that this works in the first equation if we want to make sure we did not make a mistake.

Answer 3

Thank you! :D

Answer 4

yw