Robert believes the lines graphed at right are perpendicular, but Mario is not convinced. What is the slope of each line? Explain how you know whether or not the lines are perpendicular.

Answer/Step-by-step explanation:

An easy way to be sure two lines are perpendicular is if the product of both slopes equals -1.

That is: . Where, m1 and m2 are slopes of both lines respectively.

Let's find the slope of the both lines.

Slope of the line that slants upward from left to right using coordinates (0, 0) and (2, 2) of two points on the line:

Slope of the line that slants downwards from left to right using coordinates (2, 2) and (0, 4) of two points on the line:

Find the product of both slopes

Therefore, we know the lines are perpendicular because .