### Home > GC > Chapter 2 > Lesson 2.1.4 > Problem2-39

2-39.

Robert believes the lines graphed below are perpendicular, but Mario is not convinced. Find the slope of each line, and explain how you know whether or not the lines are perpendicular.

Remember that the slope of a line is the change in $y$ over change in $x$. Now try to solve for the slopes. One possible option is to use a slope calculator.