Question

Given the system of equations presented here:

4x + y = 4
2x + 7y = 28

Which of the following actions creates an equivalent system such that, when combined with the other equation, one of the variables is eliminated?

Multiply the second equation by −1 to get −2x − 7y = −28
Multiply the second equation by −4 to get −8x − 28y = −112
Multiply the first equation by −7 to get −28x − 7y = −28
Multiply the first equation by −2 to get −8x − 2y = −8

Answer 1

what do you think?

Answer 2

I really don't know, that's why I need help

Answer 3

Okedoke

you are looking for the answer that will change one equation in a way that makes either x y or = cancel out with the other equation.

for example if one equation is:

5x + 7y = 28 and the second one is
-5x +6y = 100

the variable that cancels out is X. because -5 and 5

Answer 4

Okay, so would it be D because if it is multiplied by -2 the x would cancel out?

Answer 5

so in your case the only equation that would make either x,y or = cancel out is the third one because:

-28x -7y = -28
2x + 7y =28

see how the y variable cancelled?

Answer 6

Oh okay, thank you

Answer 7

it actually cancels y and the =