$\cos\left(x\right)\cdot\left(\sec\left(x\right)+\cos\left(x\right)\cdot\csc\left(x\right)^2\right)=\csc\left(x\right)^2$

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

$12x^2-27$

$9^3.9^2$

$\frac{6}{x}=x+5$

$16z^{2}-56z+49$

$\frac{dy}{dx}=\frac{1}{y+x^2y}$