$81y^2+18yz+z^2$

$x^2-x-1x\cdot2x-1$

$-89+\left(-1\right)$

$\left(t-2\right)\left(t+7\right)$

$\frac{20}{9}m^5-\frac{5}{2}m^3$

$\left(\frac{3}{n}-\frac{3}{n}\right)^2\:-1$

$\tan\left(\infty\right)+\frac{\cos\left(\infty\right)}{1+\sin\left(\infty\right)}=\sec\left(\infty\right)$