$\left(\frac{2}{5}x^2+3y^3\right)\left(\frac{2}{5}x^2-3y^3\right)$

$\frac{45a^2-15a-5}{-5a}$

$\lim_{x\to0}\left(\frac{3sin\left(-2x\right)}{x}\right)$

$2x^2-24x+2y^2+12y+60=0$

$\left(\frac{2}{3}y-\frac{1}{3}x\right)\left(\frac{1}{3}x+\frac{2}{3}y\right)$

$x^3+2x^2-14x-3=x^2-3$

$\lim_{x\to7}\left(\frac{cosx}{1-sinx}\right)$