Монгол Бодлогын Сан

$f(x,y)=\left({\dfrac{2x+3y}{2x-3y}-\dfrac{2x-3y}{2x+3y}}\right):\left({\dfrac{2x+3y}{2x-3y}+\dfrac{2x-3y}{2x+3y}}\right)$ байг. $f(x,y)$-ийг хялбарчилбал $f(x,y)=\dfrac{\fbox{ab}xy}{\fbox{c}x^2+\fbox{d}y^2}$ болно. Иймд $f(1-\sqrt{2},1-\sqrt{2})=\dfrac{12}{\fbox{ef}} \mbox{гарна.}$