Hi

How should I solve this:

Check these two functions continuity:

$\displaystyle

f(x,y)=

\left\{

\begin{array}{lr}

\frac {x^3-y^3}{x-y}&x \neq y\\

{x^2+xy+y^2}&x = y

\end{array}

\right.$

$\displaystyle

f(x,y)=

\left\{

\begin{array}{lr}

\frac {x^3y^2}{x^6+y^4}&(x,y) \neq (0,0)\\

0&(x,y) = (0,0)

\end{array}

\right.$

Thank you very much