$\sqrt[2]{448x^2}$

$x^2\frac{dy}{dx}+2xy=1$

$16-x^2=9x^2-24x+16$

$-x^2+6x-8$

$\frac{dy}{dx}=\cos\left(12x\right)$

$\sin\left(\frac{4\pi}{21}\right)\cos\left(\frac{\pi}{21}\right)+\cos\left(\frac{4\pi}{21}\right)\sin\left(\frac{\pi}{7}\right)$

$5.\left(12-9\right)+3\:.\:\left(19-16\right)$