$\int7cos8xcos3xdx$

$\frac{x^2-5x+6}{x^2+9x+18}$

$9\left(a+9\right)^2-6\left(a+9\right)+1$

$\left(cos\left(y\right)-ycos\left(x\right)\right)dx-\left(sen\left(x\right)+xsen\left(y\right)\right)dy=0$

$=\cos^2x+3\cos x-4$

$\lim_{x\to2}\left(3x^2-5\right)-\left(-2x+1\right)$

$x\sqrt{x^2}+1$