$\left(9a+7x^3\right)\left(9a-7x^3\right)$

$\left(8xy+7z^2\right)\left(8xy-7z^2\right)$

$\left(a+b\right)^3=a^3+3a^2\:b+3ab^2+b^3$

$\frac{\sin3\left(x\right)+\sin5\left(x\right)}{\cos3\left(x\right)-\cos5\left(x\right)}=\cot\left(x\right)$

$\frac{6x^2-2x-1}{4x^3-x}$

$\left(8x^{5}+4b^{2}\right)^{3}$

$+8+4+3+5+2$