Slope-intercept form: y = mx + b
(m is the slope, b is the y-intercept or the y value when x = 0 --> (0, y) or the point where the line crosses through the y-axis)
For lines to be perpendicular, their slopes have to be negative reciprocals of each other (flip the sign +/- and the fraction/switch the numerator and the denominator)
For example:
Slope = -2 or
Perpendicular line's slope:
(flip the sign from - to +, and flip the fraction)
Slope = ![\frac{1}{3}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7B3%7D)
Perpendicular line's slope =
or -3 (flip the sign from + to -, flip fraction)
y = 8x - 2 The slope is 8, so the perpendicular line's slope is
.
Now that you know the slope, substitute/plug it into the equation:
y = mx + b
To find b, plug in the point (-5, -6) into the equation, then isolate/get the variable "b" by itself
(Two negative signs cancel each other out and become positive)
Subtract 5/8 on both sides to get "b" by itself
(To combine fractions, they need to have the same denominator, so multiply -6 by 8/8 so that they will have the same denominator)
![(\frac{8}{8}) (-6)-\frac{5}{8} =b](https://tex.z-dn.net/?f=%28%5Cfrac%7B8%7D%7B8%7D%29%20%28-6%29-%5Cfrac%7B5%7D%7B8%7D%20%3Db)
= b Now combine the fractions
![-\frac{53}{8} =b](https://tex.z-dn.net/?f=-%5Cfrac%7B53%7D%7B8%7D%20%3Db)
![y=-\frac{1}{8} x-\frac{53}{8}](https://tex.z-dn.net/?f=y%3D-%5Cfrac%7B1%7D%7B8%7D%20x-%5Cfrac%7B53%7D%7B8%7D)