Problem

For each pair of functions $f$ and $g$ below, find $f(g(x))$ and $g(f(x))$. Then, determine whether $f$ and $g$ are inverses of each other. Simplify your answers as much as possible. (Assume that your expressions are defined for all $x$ in the domain of the composition. You do not have to indicate the domain.) (a) \[ \begin{array}{l} f(x)=\frac{3}{x}, x \neq 0 \\ g(x)=\frac{3}{x}, x \neq 0 \\ f(g(x))=\square \\ g(f(x))=\square \end{array} \] $f$ and $g$ are inverses of each other $f$ and $g$ are not inverses of each other (b) $f(x)=x+4$ \[ g(x)=-x+4 \] \[ f(g(x))= \] \[ g(f(x))= \] $f$ and $g$ are inverses of each other $f$ and $g$ are not inverses of each other

Solution

Step 1 :Given the functions \(f(x) = \frac{3}{x}\) and \(g(x) = \frac{3}{x}\), we need to find \(f(g(x))\) and \(g(f(x))\).

Step 2 :Substitute \(g(x)\) into \(f(x)\) to get \(f(g(x)) = \frac{3}{\frac{3}{x}} = x\).

Step 3 :Substitute \(f(x)\) into \(g(x)\) to get \(g(f(x)) = \frac{3}{\frac{3}{x}} = x\).

Step 4 :Since both \(f(g(x))\) and \(g(f(x))\) equal to \(x\), \(f\) and \(g\) are inverses of each other.

Step 5 :Given the functions \(f(x) = x + 4\) and \(g(x) = 4 - x\), we need to find \(f(g(x))\) and \(g(f(x))\).

Step 6 :Substitute \(g(x)\) into \(f(x)\) to get \(f(g(x)) = (4 - x) + 4 = 8 - x\).

Step 7 :Substitute \(f(x)\) into \(g(x)\) to get \(g(f(x)) = 4 - (x + 4) = -x\).

Step 8 :Since neither \(f(g(x))\) nor \(g(f(x))\) equal to \(x\), \(f\) and \(g\) are not inverses of each other.

Step 9 :\(\boxed{\text{For the first pair of functions, } f \text{ and } g \text{ are inverses of each other. For the second pair of functions, } f \text{ and } g \text{ are not inverses of each other.}}\)

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Source: https://solvelyapp.com/problems/20491/

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