Question

What is the slope of `y= -5`?

Answer 1

0.
The slope is 0.

Explanation:

Recall the definition of a slope:

`slope=(rise)/(run)`

Or

`m=(Δy)/(Δx) = (y_"2"-y_"1")/(x_"2"-x_"1")`

But since y does not increase nor decrease (y is -5 everywhere), the numerator is zero. Also note that the denominator is non-zero hence, the slope is zero.

This is the case for every horizontal line:
`y=n`, where n is real number

For vertical lines, the slope approaches infinity (since infinity isn't a number).