I've been solving various quadratic equation for some time now, and I found 2 equations that I am unable to solve:
$x^2-y^2=5 $
$\frac{1}{x}+\frac{1}{y}=-\frac{1}{6}$
This is one of the equations. The problem I have is if I exchange $y$ with and expression with $x$ I will always get $xy$, and I just can't get rid of $xy$ and I can't express $xy$ by anything else.