$5x-x^2=0$

$\int\cos\left(3x\right)^4\sin\left(3x\right)dx$

$3x^2-x-2$

$\log\left(\left(2x+5\right)^{2}\right)=4$

$\lim_{x\to5}\left(\frac{x-3}{2x}\right)^{\frac{x-3}{x}}$

$\lim_{x\to0}\left(\sqrt{2+\left(2x^2+3x+1\right)^4}\right)$

$\cos\left(\frac{\pi}{16}\right)=\frac{15}{x}$