Perpendicular lines {ACT}

In the xy-plane, line l is perpendicular to the graph of the function f(x) = 5x - 2.
Line l could be the graph of which of the following functions?
A.)  g(x) = -5x
B.)  g(x) = (-1/5)x
C.)  g(x) = x - 2
D.)  g(x) = (1/5)x
E.)  g(x) = 5x

Perpendicular lines have slopes which are negative reciprocals.

Slope-intercept form is y = mx + b
m is the slope
b is the y-intercept

f(x) = 5x - 2
y = 5x - 2 {slope-intercept form}
slope = 5 {the number in front of the x}

The line perpendicular to that would have a slope of -1/5.

B.)  g(x) = (-1/5)x has a slope of -1/5

- Algebra House