Question

For f(x)=5+1, find f(-4)

Answer 1

I think you mean f(x)=5x+1.
That would be f(-4)=5(-4)+1.
f(-4)=-20+1
f(-4)=-19

Answer 2

If you typed the whole question of f(x)=5+1, then f(x)=6
y=6
If x=-4 and y=6