Find the limit of this function?

You might not have learned this yet but if you differentiate the numerator and the denominator (separately) you'll be able to find the limit. This is called l'hopitals rule and it only works when you have an indeterminate form such as 0/0 like you have here. Also, I didn't work out the problem but looking at it it looks as though multiplying by the conjugate radical would work.