Here is the question...

Determine the points (x,y), if any, at which f(x,y) is not continuous.

a.$\displaystyle f(x,y) = \frac{x-y}{1+x^2+y^2}$

b.$\displaystyle f(x,y)=e^{x+y}+\sqrt{x+y}$

Can someone please solve these and explain to me how to go about solving them? Thanks in advance.