$$\frac{ x }{ { x }^{ 2 } +x-2 } - \frac{ 3 }{ { x }^{ 2 } +2x-3 } - \frac{ x }{ { x }^{ 2 } +5x+6 }$$
$\frac{x-6}{\left(x-1\right)\left(x+2\right)\left(x+3\right)}$
$-\frac{x\left(\left(2x-7\right)^{2}-145\right)}{2\left(\left(x-1\right)\left(x+2\right)\left(x+3\right)\right)^{2}}$