$3-\left(4+5\right)-3\cdot2$

$\sqrt{\frac{x+y}{x-y}}-\sqrt{\frac{x-y}{x+y}}$

$-5\frac{1}{2}+2\frac{3}{4}$

$\int\frac{3x^2-8x+13}{\left(x+3\right)\left(x^2-1\right)}dx$

$12+4-16+48-3$

$\frac{6x^2-31x+35}{2x-7}$

$\int_{\frac{-\pi}{2}}^{\frac{\pi}{2}}x\cos\left(2nx\right)dx$