K = \(\left(\frac{x+2}{3x}+\frac{2}{x+1}-3\right):\frac{2-4x}{x+1}-\frac{3x+1-x^2}{3x}=\left(\frac{\left(x+1\right)\left(x+2\right)}{3x\left(x+1\right)}+\frac{2.3x}{3x\left(x+1\right)}-\frac{3.3x\left(x+1\right)}{3x\left(x+1\right)}\right).\frac{x+1}{2\left(1-2x\right)}-1+\frac{1}{3x}-\frac{x}{3}-1=\frac{-2\left(4x^2-1\right)}{3x}.\frac{1}{-2\left(2x-1\right)}+\frac{1+x^2}{3x}-1=\frac{-2\left(2x-1\right)\left(2x+1\right)}{3x}.\frac{1}{-2\left(2x-1\right)}+\frac{1+x^2}{3x}-1=\frac{2x+1}{3x}+\frac{1+x^2}{3x}-1=\frac{\left(x+1\right)^2}{3x}-1\)
