# Video: Evaluating Composite Functions at a Given Value

If π(π₯) = 3 β π₯Β² and π(π₯) = 2π₯ + 4, find (π β π)(1).

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### Video Transcript

If π of π₯ equals three minus π₯ squared and π of π₯ equals two π₯ plus four, find π of π of one.

What weβre doing is weβre completing the composition of functions. So we can rewrite this in a way that might make a little more sense. It can be written as π of π of one. Itβs said the same way, but written a little bit differently. So essentially, we plug one into the π function, and then whatever we get for that, we will take that number and plug it into the π function.

So first, letβs plug one into the π function for π₯. So instead of two π₯ plus four, itβs two times one plus four; weβre plugging in one. And two times one is two plus four is six. So now weβre gonna plug six into the π of π₯ function, so we have three minus six squared, and three minus 36 is equal to negative 33.