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

$\frac{cos\left(45\right)+cos\left(60\right)}{sin\left(45\right)-sin\left(30\right)}$

$\frac{dy}{dx}=-3x^{\frac{2}{5}}$

$x\left(2\right)+18x+81$

$2\sin^2x+7\sin x+3=0$

$\lim_{x\to x}\left(\frac{2x^3-2x^2+x-3}{x^3+2x^2-x+1}\right)$

$\frac{6}{3x+5},\:c=0$