Is a horizontal line a function?

Consider the function f(x)=-5x+3 what is f(-2)

Ineed i been stuck on this question since yesterday

Which function can be used to model the monthly profit for x trinkets produced? f(x) = –4(x – 50)(x – 250) f(x) = (x – 50)(x – 250) f(x) = 28(x + 50)(x + 250) f(x) = (x + 50)(x + 250)