Let f and g be integrable functions on [a,b]. Prove that thye absolute value of the ∫fg from a to b ≤(∫f^2 fro?

Let f and g be integrable functions on [a,b]. Prove that thye absolute value of the ∫fg from a to b ≤(∫f^2 from a to b)^1/2(∫g^2 from a to b)^1/2.