$2x^2+3xy-4x$

$\lim_{x\to0}\left(\frac{sin\left(x^2-4\right)}{x-2}\right)$

$a^2+2\cdot2a+2^2$

$-\left(-32\right)-66-\left(-28\right)$

$2\cot\left(x\right)^2+5\cot\left(x\right)-3=0$

$\lim_{x\to0}\left(\frac{1-\cos\left(6x\right)}{3x^2}\right)$

$\frac{6-3\sec^2\left(x\right)}{\sec^2\left(x\right)}$