# For F(x) = -4x how do you find f(0)?

I'd say $- 4$, unless $F \left(x\right) = f \left(x\right)$ then $f \left(0\right) = 0$.
If $F \left(x\right) = - 4$, then $f \left(x\right) = \frac{d}{\mathrm{dx}} \left(F \left(x\right)\right) = - 4$.
But since this is algebra, I'll assume that $F \left(x\right) = f \left(x\right)$. In that case, $f \left(0\right) = - 4 \cdot 0 = 0$.