h(h(x)) = [tex]x^{4}[/tex] + 6x² + 12
f(f(x)) = x
note that h ○ h = h(h(x))
To evaluate substitute h(x) into h(x)
h(h(x)) = h(x² + 3 ) = (x² + 3 )² + 3 = [tex]x^{4}[/tex] + 6x² + 9 + 3 = [tex]x^{4}[/tex] + 6x² + 12
Similarly for f ○ f
f(f(x)) = f([tex]\frac{9}{2x}[/tex])
= 9 / (2 × [tex]\frac{9}{2x}[/tex] = 9 / [tex]\frac{9}{x}[/tex] = [tex]\frac{9x}{9}[/tex] = x
