$\left(9-x\right)\left(4+x^3\right)$

$\int_1^{\infty}\left(\frac{1}{9x+4}\right)dx$

$3y''-6y'+6y=0$

$-81-1$

$\int\left(\frac{2x-1}{x^2+x}\right)dx$

$\frac{1}{\sin x\cot\left(x\right)}-\frac{1}{\cos\left(x\right)}$

$\cos\left(u\right)\sec\left(u\right)-\sin^2\left(u\right)=\cos\left(u\right)$