Question

Which of these strategies would eliminate a variable

in the system of equations?
-7x + 2y = 5
3x - 5y = -5
Choose all answers that apply:
Multiply the top equation by 3, multiply the bottom
equation by 7, then add the equations.
Multiply the top equation by 5, multiply the bottom
equation by 2, then add the equations.
Add the equations.

Answer 1

Multiply the first equation by 3

Multiply the second equation by -7

Explanation:

After doing the above method, you will derive equation 3 and 4 then you can eliminate the x and get y .

FURTHER EXPLANATION

`-7x + 2y = 5 -------(1)\\3x - 5y = -5-------(2)\\\\-7x + 2y = 5 -------(1) * 3\\3x - 5y = -5-------(2)*-7\\\\-21x +6y=15 -----(3)\\-21x +35y=35----(4)\\Subtract -eq- 4- from -eq- 3 \\-29y =-20\\Divide-both-sides-by;-29\\(-29y)/(-29) =(-20)/(-29) \\y = 20/29\\`

`Substitute ; 20/29 for y- in- eq 1\\-7x + 2y = 5----(1)\\-7x +2(20/29) = 5\\-7x +40/29=5\\-7x = 5 - 40/29\\-7x = 105/29\\Divide through by -7\\x = -15/29`

I Hope It helps

Answer 2

Multiply the first equation by 3

Multiply the second equation by -7

Explanation:

`( - 7x + 2y = 5) * 3 \\ (3x - 5y = - 5) * 7`

`- 21x + 6y = 15 ..(3)\\ - 21x - 35y = - 35...(4)`

Subtract equation 3 from equation 4

`- 21x - ( - 21x) = - 21x + 21x = 0`

x has been eliminated