EJC Functions Tutorial Q11

EJC Functions Tutorial Q11

Tutorial

The function \(\mathrm{f}\) is defined by

\(\mathrm{f}\left( x \right)=\left\{ \begin{matrix}{{x}^{2}}+1, & \mathrm{for }x\ge 0\\ 2x+1, & \mathrm{for }x<0 \end{matrix} \right.\)

Sketch the graph of \(\mathrm{f}\). Show that \({{\mathrm{f}}^{-1}}\) exists and define it. Sketch the graph of \({{\mathrm{f}}^{-1}}\) on the same diagram as the graph of \(\mathrm{f}\), and find the value of \(x\) for which \(\mathrm{f}\left( x \right)={{\mathrm{f}}^{-1}}\left( x \right)\).

Given \(\mathrm{g}\left( x \right)={{x}^{2}}-2\), \(x\in \mathbb{R}\), find \(\mathrm{gf}\left( x \right)\).

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Answer:Given \(x=-1\(, \)\therefore \mathrm{gf}\left( x \right)=\left\{ \begin{matrix}{{\left( {{x}^{2}}+1 \right)}^{2}}-2, & \mathrm{for }\!\!~\!\!\mathrm{ }\,\,\,x\ge 0 \\ {{\left( 2x+1 \right)}^{2}}-2, & \mathrm{for }\!\!~\!\!\mathrm{ }\,\,\,x<0 \\\end{matrix} \right.\):

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