f[g(x)] = h(x)

f[x^2 + 3] = x^4 + 6x^2 + 20

substitute y = x^2

f[x^2 + 3] = y^2 + 6y + 20

factor

f[x^2 + 3] - 11 = y^2 + 6y + 9

f[x^2 + 3] - 11 = (y + 3)^2

f[x^2 + 3] = (y + 3)^2 + 11

plug back in

f[x^2 + 3] = (x^2 + 3)^2 + 11

f(x) = x^2 + 11

borrringggg