$\left(-3x+9\right)-\left(-2x^2+6x\right)$

$3,025+0,21$

$42x^{\left(5\right)}y^{\left(2\right)}+7x^{\left(3\right)}y^{\left(7\right)}-9x^{\left(6\right)}y$

$r^4\:\left(-5\right)r^3$

$\left(x+-6\right)\left(x+5\right)+\left(x+2\right)\left(x-1\right)$

$\left(6x^2+8y\right)\left(6x^2-8y\right)$

$-\left[\:\left(-5\:+4\right)\:-\:\left(-8\:-7\right)\:+\:\left(-8+4\right)\right]$