I need to determine how to fina a missing variable. For example, kx-8+7y=0 if it will be parallel to the equation 2x-y+1=0. I need it a.s.a.p. thank you!

I'm not sure with the answer k=-2

Uh... no, that's not the answer. I'll show you.

Did you notice that part?


if it will be parallel to the equation 2x-y+1=0

The lines being equal means that they have the same gradient. The long path is to find the gradient of the given line, then find the gradient of the first line, then equate the gradients.

But there's a shorter way to get it. Arrange the equations in the form ay=bx+c.

1.
kx-8+7y=0

7y=-kx+8

2.
2x-y+1=0

2x+1=y

y=2x+1

Now, multiply the second equation by 7;

7 \times (y)=7 \times (2x+1)

7y=14x+7

You see them now?

7y=-kx+8 and 7y=14x+7

The 'y' part are the same. The c is the y-intercept, and doesn't need to be the same.

Therefore, -k=14 and k=-14

Hope it helped! :)