$4-\left(1-3\right)$

$\frac{dy}{dx}=\frac{3x+2}{2x^2-1}$

$\lim_{x\to0}\left(\frac{1-cos7x}{\left(e^{2x}-1\right)^2}\right)$

$\frac{m^4-81}{m^2-9}$

$\frac{dy}{dt}=\frac{y}{t^2-28t+147},\:y\left(14\right)=1$

$\left(7b^3-5c^4\right)\cdot\left(49^6-35b^3c^4+25c^8\right)$

$-9x=-5x$