$-6\left(9-5a\right)-4a$

$\cos\left(2\infty\right)=1-2\sin^2\left(\infty\right)$

$2x^4+x^3-11x^2+11x-3$

$1-\frac{2\tan\left(x\right)}{1-2\tan\left(x\right)}$

$\lim_{x\to\infty}\left(\frac{1.001^x}{x^{35}}\right)$

$2,5+-0,5$

$\int\frac{5x^2-x-2}{\left(x+1\right)\left(x^2+1\right)}dx$