# Another solution needed

Calculus Level 4

Let $$f$$ be a differentiable function satisfying the condition $$f(y)\cdot f(x - y) = f(x)$$

It is given that $$f'(0)=p, \quad f'(5)=q$$

Then find $$f'(-5)$$.

Details and Assumptions:-

• $$f'(x) = \dfrac{d(f(x))}{dx}$$ , $$f'(k)$$ is value of $$\frac{d(f(x))}{dx}$$ at $$x=k$$,
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