$2\:+\:\left(-4\:+\:5\right)\:-\:\left(\:6\:+\:6\right)\:+\:7\:=\:$

$4\log\:\left(\frac{x}{5}\right)+\:\log\:\left(\frac{625}{4}\right)=2\log\:\left(x\right)$

$5x^2-8x+1=0$

$3a^2+4a^3+7a^4b^2$

$2\left(x^2-3x+1\right)\left(x-1\right)$

$\lim_{x\to\infty}\left(\sqrt{x^2+2}-\sqrt{x^2-2x}\right)$

$-5y+x+6y-8x$