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Composite Functions

Functions can be chained, for example \(gf(5)\), these are called composite functions.

Example

Example functions: \(f(x) = 7x - 3\) and \(g(x) = 3x + 8\). Given these examples, \(gf(3)\) would equal \(62\).

\[ \begin{align} f(3) & = 7(3) - 3 \\ & = 21 = 3 \\ & = 18 \\ \\ g(18) & = 3(18) + 8 \\ & = 54 + 8 \\ & = 62 \\ \end{align} \]

Algebraic Example

Using the previously given example functions, you could work out a function for \(gf(x)\).

\[ \begin{align} gf(x) & = 3(7x - 3) + 8 \\ & = 21x - 9 + 8 \\ & = 21x -1 \end{align} \]

Given that \(gf(x) = 21x - 7\), you can work out \(gf(3)\) using a single function.

\[ \begin{align} gf(x) & = 21(3) - 1 \\ & = 63 -1 \\ & = 62 \end{align} \]

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