For each pair of functions [tex]f[/tex] and [tex]g[/tex] below, find [tex]f(g(x))[/tex] and [tex]g(f(x))[/tex]. Then, determine whether [tex]f[/tex] and [tex]g[/tex] are inverses of each other. Simplify your answers as much as possible. (Assume that your expressions are defined for all [tex]x[/tex] in the domain of the composition. You do not have to indicate the domain.)

(a) [tex]f(x)=-\frac{x}{6}[/tex]

[tex]\[
\begin{array}{l}
g(x)=-6x \\
f(g(x))=\square \\
g(f(x))=\square
\end{array}
\][/tex]

[tex]f[/tex] and [tex]g[/tex] are inverses of each other

(b) [tex]f(x)=2x+7[/tex]

[tex]\[
\begin{array}{l}
g(x)=\frac{x-7}{2} \\
f(g(x))=\square \\
g(f(x))=\square
\end{array}
\][/tex]

[tex]f[/tex] and [tex]g[/tex] are inverses of each other

[tex]f[/tex] and [tex]g[/tex] are not inverses of each other



Answer :

To determine whether the given pairs of functions [tex]\( f \)[/tex] and [tex]\( g \)[/tex] are inverses of each other, we need to compute [tex]\( f(g(x)) \)[/tex] and [tex]\( g(f(x)) \)[/tex]. If both compositions simplify to [tex]\( x \)[/tex], then [tex]\( f \)[/tex] and [tex]\( g \)[/tex] are indeed inverses of each other.

### Pair 1
Given:
- [tex]\( f(x) = -\frac{x}{6} \)[/tex]
- [tex]\( g(x) = -6x \)[/tex]

Finding [tex]\( f(g(x)) \)[/tex]:
[tex]\[ f(g(x)) = f(-6x) = -\frac{-6x}{6} = x \][/tex]

Finding [tex]\( g(f(x)) \)[/tex]:
[tex]\[ g(f(x)) = g\left(-\frac{x}{6}\right) = -6\left(-\frac{x}{6}\right) = x \][/tex]

Since both [tex]\( f(g(x)) \)[/tex] and [tex]\( g(f(x)) \)[/tex] simplify to [tex]\( x \)[/tex], the functions [tex]\( f(x) = -\frac{x}{6} \)[/tex] and [tex]\( g(x) = -6x \)[/tex] are inverses of each other.

### Pair 2
Given:
- [tex]\( f(x) = 2x + 7 \)[/tex]
- [tex]\( g(x) = \frac{x - 7}{2} \)[/tex]

Finding [tex]\( f(g(x)) \)[/tex]:
[tex]\[ f(g(x)) = f\left(\frac{x - 7}{2}\right) = 2\left(\frac{x - 7}{2}\right) + 7 = (x - 7) + 7 = x \][/tex]

Finding [tex]\( g(f(x)) \)[/tex]:
[tex]\[ g(f(x)) = g(2x + 7) = \frac{(2x + 7) - 7}{2} = \frac{2x}{2} = x \][/tex]

Since both [tex]\( f(g(x)) \)[/tex] and [tex]\( g(f(x)) \)[/tex] simplify to [tex]\( x \)[/tex], the functions [tex]\( f(x) = 2x + 7 \)[/tex] and [tex]\( g(x) = \frac{x - 7}{2} \)[/tex] are inverses of each other.

### Conclusion
For both pairs of functions, the compositions simplify to [tex]\( x \)[/tex]. Thus:

- For [tex]\( f(x) = -\frac{x}{6} \)[/tex] and [tex]\( g(x) = -6x \)[/tex], [tex]\( f \)[/tex] and [tex]\( g \)[/tex] are inverses of each other.
- For [tex]\( f(x) = 2x + 7 \)[/tex] and [tex]\( g(x) = \frac{x - 7}{2} \)[/tex], [tex]\( f \)[/tex] and [tex]\( g \)[/tex] are inverses of each other.