Write an equation of a line that is perpendicular to the line represented by 4x – y = 16 and goes through point (0, 4) on the y-axis.

So perp. is the slope flipped and changed signs because they have to equal to -1. so:
first you need to get it into slope intercept form:
4x - y = 16
-4x
-y = 16 - 4x
/-
y = 4x - 16
then flip and change the sign of the slope
y = -1/4x + b
add your coords
4 = -1/4(0) + b
4 = 0 + b
-0
4 = b
then make your new slope intercept form:
y = -1/4x + 4

y = -1/4x + 4