Question

What is the basic difference between the lines y = x and y = -x?

Answer 1

See explanation

Explanation:

Consider `y=x`

The count of `x's` is 1 so although it is not normally shown we actually have `y=+1x`

This number 1 is the slope (gradient) which is the amount of up or down for 1 along reading left to right on the x-axis.

As the vertical position increases (positive direction) the slope is upwards

Consider `y=-x -> y=-1x`

In this case the the vertical position decreases (negative direction) the slop is downwards.