$4cos^3x-cosx=0$

$a^2m+a^3n+ax^2$

$\lim\:_{x\to\:2}\:\frac{\left(x^3+x^2-4x-4\right)}{x^2+x-6}$

$\lim_{x\to\frac{\pi}{4}}\left(2-\tan\left(x\right)\sec\left(x\right)\right)$

$\frac{d}{dy}\left(3x\left(2y-1\right)\left(z+5\right)\right)$

$\lim_{x\to-2}\left(\frac{7x^3+14x^2}{14x^2+28x}\right)$

$20sin\left(5x\right)cos\left(5x\right)$