\(a,P=\dfrac{\left(2x+1\right)^2}{x-2}\cdot\dfrac{4\left(x-2\right)\left(x+2\right)}{2x+1}=4\left(2x+1\right)\left(x+2\right)\\ b,P=\dfrac{2\left(x^2+2x+4\right)}{\left(x^2-1\right)\left(x-3\right)}:\dfrac{\left(x-2\right)\left(x^2+2x+4\right)}{\left(x+1\right)\left(x-3\right)}\\ P=\dfrac{2\left(x^2+2x+4\right)}{\left(x-1\right)\left(x+1\right)\left(x-3\right)}\cdot\dfrac{\left(x+1\right)\left(x-3\right)}{\left(x-2\right)\left(x^2+2x+4\right)}\\ P=\dfrac{2}{\left(x-1\right)\left(x-2\right)}\)