I'm having trouble simplifying this equation
$\displaystyle \frac {x^2-4xy+4y^2}{x^2-y^2}$ $\displaystyle / \frac {x^2 + xy - 6y^2}{x^2+2xy+y^2}$
$\displaystyle = \frac {(x-2y)^2}{(x+y)(x-y)} / \frac {(x+3y)(x-2y)}{(x+y)^2}$
$\displaystyle =\frac {(x-2y)^2}{(x+y)(x-y)} * \frac {(x+y)^2}{(x+3y)(x-2y)}$
$\displaystyle = \frac {(x-2y)(x+y)}{(x-y)(x+3y)}$
$\displaystyle = \frac {x^2-xy-2y^2}{x^2+2xy+3y^2}$