$2\pi\left(10cm\right)\left(20cm\right)$

$\left(x-2\right)y'+y=0$

$\lim_{x\to-5}\left(\frac{\left(x^2+4x-5\right)}{\left(x^2+11x+30\right)}\right)$

$2\sen^{2}x+3\cos x=0$

$9\int\left(sin\left(ln\left(5x\right)\right)\right)dx$

$\lim_{x\to\infty}\left(\frac{\left(-2x-1\right)\left(x+3\right)^2}{\left(x+4\right)^2\left(x-7\right)}\right)$

$25\:-\:16x^2$