Question

Which of the following statements are FALSE when identifying the type of slope of a line.

A Positive slope increases from left to right.
B Negative slope decreases from left to right.
C Undefined slope is when there is no vertical change.
D No or Zero slope is a horizontal line.

Answer 1

Answer: Choice C) Undefined slope is when there is no vertical change

If you replace "vertical" with "horizontal", then choice C would be a true statement. All vertical lines have an undefined slope.

This is because the slope formula

m = (y2-y1)/(x2-x1)

has 0 in the denominator when you subtract the x coordinates. Dividing by zero is undefined. For any single vertical line, the x coordinates of any two points are the same. For instance, the vertical line through 4 on the x axis is the equation x = 4, and every point on this line has x coordinate 4.