Question

How do you find the slope & y-intercept of the equation `x = –9`?

Answer 1

The slope is undefined.
There is no `y-`intercept.

Explanation:

The equation of a straight line in slope (`m`) and `y-`intercept (`c`) form is : `y=mx +c`

In this case: `x=-9` is a vertical straight line through the point `(-9,0)` parallel to the `y-`axis.

By definition, the slope of a vertical line is undefined. Also, since it will never intersect the `y-`axis there is no `y-`intercept.

We can see this from the graph of `x=-9` below.

graph{0.0001y + x=-9 [-16.02, 16.02, -8.02, 8]}