# What is the slope of any line perpendicular to the line passing through (1,-2) and (-8,1)?

The slope of the line passing through (1,-2) and (-8,1) is = $\frac{{y}_{2} - {y}_{1}}{{x}_{2} - {x}_{1}}$ or $\frac{1 + 2}{- 8 - 1} = - \frac{1}{3}$
So the slope of the perpendicular line is $- \frac{1}{- \frac{1}{3}} = 3$. Since the condition of perpendicularity of two lines is product of their slopes will be equal to -1