Question

Line CD contains points A (4, −7) and B (4, 8). The slope of line CD is

zero

undefined

positive

negative

Answer 1

Do you know slope formula?

Answer 2

It is:\[\frac{ y _{2}-y _{1} }{ x _{2}-x _{1} }\]which is rise over run.

Answer 3

You get these x and y values from your two points (coordinates). y2 is 8, y1 is -7, x2 is 4, and x1 is 4. So the equation is set up like this...

Answer 4

\[\frac{ 8-4 }{ 4-4 }=\frac{ 4 }{ 0 }\]And of course you know that having a 0 in the denominator of a fraction is mathematically illegal, so the slope is undefined. That means that it is a straight up and down line.