$2\cos\left(2u\right)=4\cos^2\left(u\right)-2$

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

$\left(\frac{1}{4}x\left(3\right)-\frac{1}{3}\right)^2$

$\int_0^{\infty}\left(\frac{1}{9+4x+x^2}\right)dx$

$\frac{dy}{dx}=3\sin\left(x\right)+5\cos\left(x\right)$

$39^2$

$\lim_{x\to0}\left(xe^{\frac{2}{x}}\right)$