sketch the graph of the inverse to the folowing functions
The meaning behind this is quite simple: the graph of the inverse function is the graph of the original function reflected over the line y = x. I can't sketch it for you, but that's the concept.
So for y=x, this is trivial. To find the inverse you essentially switch all x's and y's, so y=x is it's own inverse. You can confirm this geometrically by reflecting the graph over the line y=x.
For the second one, if you can't see how the reflection would work, use the fact that if the original graph has the point (x,y), the inverse graph has the point (y,x). Draw some points until you can the figure.