$\lim\:_{x\to\:\frac{\pi\:}{4}}\left(\frac{sec^2\:x-2}{tan\:x-1}\right)$

$\left(2t-t\right)\left(t-2\right)$

$3x^2+8x+4=0$

$2-31+17-21+89-39-7+3$

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

$-1250+-3600$

$-bn+\frac{3}{5}bn$