What is the y-intercept of the function f (x) = 4 - 5x?

The slope-intercept form of a line is

y=mx+b

where m is the slope

b is the y-intercept

if you convert the function into an equation, then

y=4-5x

rearranging the equation

y=-5x + 4

thus

m=-5 and b=4

the y-intercept of the function is 4