$4a^4-12a^2b+9b^2$

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

$-\frac{aby}{-ax}$

$\lim_{x\to\infty}\left(\frac{2x^3-2x^2+x-3}{x^3+2x^2-x+1}\right)\pi$

$\frac{5s^{-7}}{10s^{-9}}$

$\sec\left(a\right)=\tan\left(a\right)\cdot\csc\left(a\right)$

$\lim_{x\to2}\left(\frac{x-2\cos\left(\pi x\right)}{x^2-4}\right)$