# What is the slope of any line perpendicular to the line passing through (-9,8) and (-1,1)?

May 20, 2018

$m ' = \frac{8}{7}$

#### Explanation:

First find the slope of this line:

$m = \frac{{y}_{2} - {y}_{1}}{{x}_{2} - {x}_{1}}$

$m = \frac{1 - 8}{- 1 - \left(- 9\right)}$

$m = - \frac{7}{8}$

formula for a perpendicular slope is $m ' = - \frac{1}{m}$

$m ' = - \frac{1}{- \frac{7}{8}} = \frac{8}{7}$

May 20, 2018

$\frac{8}{7}$

#### Explanation:

find the slope of the two given points
from the two points slope formula:

$m = \frac{{y}_{2} - {y}_{1}}{{x}_{2} - {x}_{1}}$

$\left(- 9 , 8\right) \text{ and } \left(- 1 , 1\right)$

${x}_{1} = - 9$

${x}_{2} = - 1$

${y}_{1} = 8$

${y}_{2} = 1$

$m = \frac{1 - 8}{- 1 - \left(- 9\right)} = - \frac{7}{8}$

perpendicular slope means the reciprocal in the opposite sign

so $\frac{8}{7}$