+41 Given that $a > 0$, if $f(g(a)) = 8$, where $f(x) = x^2 + 8$ and $g(x) = x^2 - 4$, what is the value of $a$?
+36916 Start with f(x) = 8 where x , in this case is g(a)
f(x) = 8
x^2 + 8 = 8
x = 0 rememeber that x is g(a) in this case, so a^2 - 4 =0
a^2 - 4 = 0
a^2 = 4
a = +-2
