# Derivative of a Product of Functions

Use the product rule whenever there is a function that's a product of two other functions of *x*. If

*f*(*x*) = ({something with an *x*}) × ({something else with an *x*}),

then use the product rule to find *f*'.

To use the product rule, figure out which two functions are multiplied together, and the derivative of each of those functions.

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