$b^2-16$

$\left(4m^2-7n^4\right)\left(4m^2+7n^4\right)$

$\frac{d^2}{dx^2}\ln\left(2x+3y\right)$

$\left(6a\:+7b\:-2c\right)\:+\left(2a-7b+2c-1\right)$

$\int\frac{3x^3+5x}{x^2+x-2}dx$

$\int r^2\left(\frac{r^3}{21}+7\right)^6dr$

$\frac{\sin\left(-a\right)}{\tan\left(-a\right)}$