$\lim_{x\to0}\left(\frac{x}{x-1}-\frac{1}{ln\left(x\right)}\right)$

$7\left(-9\right)\left(4\right)$

$-8x+13-12x+12-x$

$\frac{\tan\left(a\right)+\sec^3\left(a\right)-\sec\left(a\right)}{\sec\left(a\right)}=\tan^2\left(a\right)+\sin\left(a\right)$

$\left(\frac{1}{y^2}-\frac{2}{y^4}\right)\left(y+6y^3\right)$

$cot\left(x\right)=cos\left(x\right)sin\left(x\right)+cos^3\left(x\right)csc\left(x\right)$

$\left(x^2+1\right)\frac{dy}{dx}=x\left(y^3+y\right)$