Question

How can I replace the underscores with numbers so the system has only one solution?:
y=4x+7
_y=_x+_

Answer 1

In order for the system to have only one solution, the lines given by the equations must intersect at only one point.

Two examples would be:

y=4x+7 and y=-4x+7

as well as

y=4x+7 and -y=4x+7

Answer 2

How do you know these two equations only intersect at only point? It is if the lines have the same x or y intercept, but the oposite sign?

Answer 3

Those were just two examples.

What I did, though, was replace "x" with "-x." Doing so reflects the graph of y=4x+7 over the y-axis.

Answer 4

Thanks!