Nomor 8 tolong yaaaa

Nomor 8 tolong yaaaa

$(fog)(x) = f(g(x)) \ = 5 {(g(x))}^{2} + 1 \ = 5 {( frac{1}{x} + 1)}^{2} + 1$

$(fog)(a) = 5 {( frac{1}{a} + 1) }^{2} + 1 \ 21 = 5 {( frac{1}{a} + 1) }^{2} + 1 \ 20 = 5 {( frac{1}{a} + 1) }^{2} \ frac{20}{5} = {( frac{1}{a} + 1) }^{2} \ 4 = {( frac{1}{a} + 1) }^{2} \ {2}^{2} - {( frac{1}{a} + 1) }^{2} = 0 \ (2 + frac{1}{a} + 1)(2 - frac{1}{a} - 1) = 0 \ ( frac{1}{a} + 3)( 1 - frac{1}{a} ) = 0 \ a = - frac{1}{3} : atau : a = 1$