Question

a system of equations is shown below.

which operations on the system of equations will isolate the y quantity?

a) multiply the second equation by 2 and add the result to the first equation

b) multiply the first equation by -7 and the second equation by -5 and add the resulting equations

c) multiply the second equation by -2 and add the result to the first equation

d) multiply the first equation by 7 and the second equation by -5 and add the resulting equations

Answer 1

I: 4x-5y=-10
II: 2x-7y=4

c) multiply the second equation by -2 and add the result to the first equation
II*-2=-4x+14y=-8

add I+II*-2: 4x-5y+(-4x+14y)=-10-8
=9y=-18