$x\frac{dy}{dx}-4y=0,\:y\left(0\right)=k$

$144b^4-120b^2c^2+25c^4$

$f\left(x\right)=\frac{1}{2}-2$

$\int\left(\frac{2}{\sqrt[5]{x}}-1\right)^2dx$

$x\left(x+1\right)+2<x\left(x-3\right)$

$\lim_{u\to\frac{\pi}{4}}\left(\frac{5\tan\left(u\right)-5\cot\left(u\right)}{2u-\frac{\pi}{2}}\right)$

$x^2-4x+21\ge0$