For the first one, you have the average value of the function over the interval . But, there is not really any simplification you can do.
For the second one, a Riemann sum looks like this:
In general, and .
So, instead of factoring out , you should only factor out . So, you want . The hint is to factor out . So, that must be :
That means . Since the square root does not have a sum inside, it appears that . Can you figure out the rest?