Question

Solve the system using the addition method.

–5x – 9y = 28
–4x + 5y = –2

A. (–2, –2)
B. (7, –4)
C. (7, 6)
D. (–11, 3)

Answer 1

Option A

Explanation:

–5x – 9y = 28 Equation 1

–4x + 5y = –2 Equation 2

We to eliminate one of the variables. In this case "Y" by using the appropiate number, in this case
`(9)/(5)`

–5x – 9y = 28

`(9)/(5)`*{–4x + 5y = –2

We have:

–5x – 9y = 28

`(-36)/(5)X +9Y=-(18)/(5)`

We have:

–5x = 28

`(-36)/(5)X =-(18)/(5)`

So, We have:

`(-36)/(5)X -5X=-(18)/(5)+28`

-61X= 122

`X=-(122)/(61)=-2`

Using Equation 2. We have:

-4*(-2)+5Y=-2

8+5Y=-2

5Y=-10

Y=
`(-10)/(5) =-2`

Finally:

X=-2

Y=-2