If f(x)=4 then f'(-10)=?

Answer 1

zero

derivative of a constant is always zero

f'(-10) = f'(2000) = f'(27) =0 if f(x) = a constant

f(x)=4 graphically is a flat, horizontal line, y=4. It has slope = 0. the slope = the derivative = f'(-10)