$\left(ax-y\right)+\left(3x+by\right)-\left(4x+5y\right)=7x+6y$

$3cos\:2x\:=\:5$

$\frac{5}{2x-3}-\frac{2}{2x+1}+\frac{4x}{14x^{2\:}}$

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

$\lim_{x\to\infty}\left(x\cdot\ln\left(\frac{x}{x+1}\right)\right)$

$x3+10x^2+31x+30$

$x^2\left(x^2-1\right)$