$\left(\cos\left(x\right)\cos\left(y\right)-\cot\left(x\right)\right)dx-\left(\sin\left(x\right)\sin\left(y\right)\right)dy=0$

$64-16x^5+x^{10}$

$25m^4-100n^2$

$x^2-4x^2+\frac{x}{x}$

$\left(3y+4z\right)\left(3y-4z\right)$

$25m^2+130mn+169n^2$

$\left(3x^3y^2-7x^2y^3\right)$