[tex] c.\ f(x)=\dfrac{18}{x}-9\ \text{and}\ g(x)=\dfrac{18}{x+9}\\\\\text{in f(x), solve for x}\\\\\dfrac{18}{x}-9=y\ \ \ \ |+9\\\\\dfrac{18}{x}=y+9\\\\\dfrac{18}{x}=\dfrac{y+9}{1}\ \ \ \ |\text{cross multiply}\\\\x(y+9)=18\ \ \ \ |:(y+9)\\\\x=\dfrac{18}{y+9}\to f^{-1}(x)=\dfrac{18}{x+9} [/tex]
