Write an equation for a line g(x) perpendicular to f(x) = 4x − 5 and passing through the point (4, 20).

The slopes of perpendicular lines are negative reciprocals.The slope of the given line is 4.The slope of the perpendicular is -1/4.
Now we need to find the equation of a line that has slope -1/4 and passes through the point (4, 20).
We use the point-slope form of the equation of a line, where m = slope, and the point is (x1, y1).
y - y1 = m(x - x1)
y - 20 = -1/4(x - 4)
-4y + 80 = x - 4
x + 4y = 84