Question

AB passes through the points (1,3) and (3,17). If CD is perpendicular to AB, what is the slope of CD?​

Answer 1

First of all, we need the slope of AB, which we can compute as

$m_{AB} = \dfrac{\Delta y}{\Delta x} = \dfrac{17-3}{3-1}=\dfrac{14}{2} = 7$

Now, if a line is perpendicular to a given line, their slopes follow this equation:

$m_{AB}m_{CD} = -1 \iff m_{CD} = -\dfrac{1}{m_{AB}}$

So, the slope of CD is -1/7