Làm tính trừ : xy/x^2 - y^2 - x^2/ y^2 - x^2

* Hướng dẫn giải

$\frac{\mathrm{xy}}{{\mathrm{x}}^2-{\mathrm{y}}^2}-\frac{{\mathrm{x}}^2}{{\mathrm{y}}^2-{\mathrm{x}}^2}=\frac{\mathrm{xy}}{{\mathrm{x}}^2-{\mathrm{y}}^2}+\frac{{\mathrm{x}}^2}{{\mathrm{x}}^2-{\mathrm{y}}^2}=\frac{\mathrm{xy}+{\mathrm{x}}^2}{{\mathrm{x}}^2-{\mathrm{y}}^2}=\frac{\mathrm{x}\left(\mathrm{x}+\mathrm{y}\right)}{\left(\mathrm{x}-\mathrm{y}\right)\left(\mathrm{x}+\mathrm{y}\right)}=\frac{\mathrm{x}}{\mathrm{x}-\mathrm{y}}$