$-\frac{b}{2}+10,\:b=6$

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

$16a^4-40a^2b+25b^2$

$\left(-8xy\right)\cdot\left(7ax\right)$

$\frac{d^4}{dx^4}\left(\sin\left(4x^2\right)\right)$

$\frac{10x^5+20x^3+5x}{5x}$

$\lim_{x\to1}\left(\frac{1-\cos\left(x-1\right)}{ln^2x}\right)$