$4\cdot\left(-5\right)-23$

$10\cdot\left(3+4\right)$

$\lim_{x\to\frac{a}{2}}\left(\frac{1-senx}{1+cos2x}\right)$

$\int\frac{\left(x^2+3x+2\right)}{2x}dx$

$\left(-3^4\right)\cdot\left(5^2\right)$

$\left(107-540+2244\right)$

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