$4a-9b+\frac{4b^3}{a^2}-\frac{9a^3}{b^2}$

$\left(1\right)-\left(-11\right)$

$\frac{d}{dx}\left(\frac{2}{x}-\frac{1}{x^2}\right)$

$\lim_{x\to-0.5}\frac{sin3x}{tan2x}$

$\lim_{x\to0}\left(\frac{tan\left(16x\right)}{sin\left(4x\right)}\right)$

$x^2+6x-3=0$

$2\cos^2x-4\cos x-3$