Product Rule for Derivatives

Let $$f \left({x}\right), j \left({x}\right), k \left({x}\right)$$ be continuous real functions.

Let $$f \left({x}\right) = j \left({x}\right) k \left({x}\right)$$.

Then $$f^{\prime} \left({x}\right) = j \left({x}\right) k^{\prime} \left({x}\right) + j^{\prime} \left({x}\right) k \left({x}\right)$$.

Proof
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