<s>[INST] What should be the method for solving and solution of $\frac{x^2+y^2}{x^2-y^2}$? If $\frac{x+y}{x-y}=3$
then $\frac{x^2+y^2}{x^2-y^2} = ?$
 [/INST] Hint :
$$
z = \frac xy \Rightarrow \frac{z+1}{z-1} = 3
$$
$$
\frac{x^2+y^2}{x^2-y^2} = \frac{z^2+1}{z^2-1} = ?
$$
</s>