$18mx-6my+54nx-18ny$

$\log_a\left(x+y\right)+\log_a\left(x-y\right)$

$\frac{dy}{dx}-2y=x^2+5$

$2x-6y-2x-3y+10$

$\sec\left(x\right)^2+\tan^2\left(x\right)=1$

$\left(-4\right)\cdot\left(-3\right)+\left(-1\right)\cdot4$

$\left(x+3\right)\left(x-4\right)+6\left(x^2-2\right)$