Use the slope formula to find the slope of line r m = (y2-y1)/(x2-x1) m = (4-11)/(10-2) m = -7/8
The slope of line r is -7/8
Now we take the negative reciprocal. In other words, we flip the fraction and flip the sign from negative to positive.
Flip the fraction: -7/8 ---> -8/7 Flip the sign: -8/7 ----> +8/7
The slope of line s is 8/7
Note how multiplying the slope of line r (-7/8) and the slope of line s (8/7) yields -1. Multiplying any two perpendicular slopes leads to a product of -1. This is excluding vertical lines as the slope is undefined.
