$-5b-3b-4b-7b$

$3x^2+x^2+x\:$

$\lim\:_{x\to\:\infty\:}\left(\frac{16in\left(n^{-4}+2\right)}{n^{-4}}\right)$

$\lim_{x\to0}\left(\frac{x^2}{x^2+1}\right)$

$\frac{dz}{dx}=x\left(3x^2\:-9\right)$

$\sin\left(x\right)\tan\left(x\right)-\sec\left(x\right)=-\cos\left(x\right)$

$3s^3-s^2+15s-5$