For the first one, you just simply divide both sides of the fraction by :

This turns the limit into:

Now we use the property that the limit of a quotient is the quotient of the limits:

The numerator goes to 0 and the denominator goes to 4, so that:

As for the second one, it involves multiplication by , but it requires a little thought, basically that:

You use that and solve it exactly as I solved the first one and you should get it.