$6a-8b+3c-6a+5b-2c-3a-4b+4c$

$\tan\left(x\right)\cdot\sec^2\left(x\right)=\sin\left(x\right)\cdot\sec^2\left(x\right)$

$3ab-\left\{3a-\left(-5ab+8a\right)-2a\right\}$

$-x^3+7x^2-15x+10$

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

$\lim_{n\to0}\left(\frac{x^3n^3}{e^{x^3n^3}}\right)$

$\left(5+a\right)\left(5-a\right)$