Answer
$f(3,1)=6$
Work Step by Step
As we are given that $\lim\limits_{(x,y) \to(a,b)}f(3,1)=6$
In general, we use the notation $\lim\limits_{(x,y) \to(a,b)}f(x,y)=L$ to indicate the values of $f(x,y)$ approach the number L as the point $(x,y)$ approaches the point $(a,b)$ along any path that stays in the domain of $f$.
A function of two variables is continuous at $(a,b)$ if
$\lim\limits_{(x,y) \to(a,b)}f(x,y)=f(a,b)$
$\lim\limits_{(x,y) \to(3,1)}f(x,y)=f(3,1)$
Hence, $f(3,1)=6$
