What would g(sqrt(f)) = equal?

Question

If a positive real number, find the following value for the function given below. g(x) = (15x)/(x ^ 2 + 3)

Answer 1

g(x) = 15x(x^2 + 3)

g(sqrf) = 15sqrf((sqrf)^2 + 3)

= 15sqrf(f + 3)

= 15f^(3/2) + 45f^(1/2)

Answer 2

Just plug in "√f" wherever you see "x"