$51\cdot45$

$\frac{cot\left(x\right)+\sec^2\left(x\right)}{\csc^2\left(x\right)}$

$\sqrt{15-2x}=x$

$\left(x^3y^2-2y^2\right)^2$

$\left(-2\right)\:-\:\left(-4\right)\:+\:\left(-5\right)\:-\:\left(-1\right)\:-\:\left(+2\right)$

$\frac{dy}{dx}\left(\frac{y-1}{x+3}\right)$

$\ln\left(x+5\right)-\ln\left(x-3\right)=\ln\left(2\right)$