How do you find the first derivative of an equation that has a minus sign, but is not solved by the product rule?

Question

Hello! I tried to find z'(x) where two functions p(x) and d(x) are used. The equation is z(x) = 7*p(x) - 4*d(x). I've tried using the product rule to solve it, but the website I'm submitting it on keeps telling me it is incorrect. Is there another rule I'm not aware of?

Answer 1

The derivative of the difference of two functions is the difference of the two derivatives.

The derivative of a constant times a function is the product of the constant and the derivative of the function.

z'(x) = 7p'(x) - 4d'(x)