$5ay-11a$

$\left(6x+3\right)\left(7x-2\right)$

$\int\left(\frac{1}{t-20}\right)dx$

$\frac{x^3+4x^2+3x}{2}$

$-2\cdot4+3$

$\frac{a^2-49b^2}{a-7b}$

$\frac{\cos\left(x\right)\cdot\cos\left(y\right)-\sin\left(x\right)\cdot\sin\left(y\right)+\sin\left(x\right)\cdot\sin\left(y\right)}{\cos\left(x\right)\cdot\sin\left(y\right)}$