a: ĐKXĐ: \(x\notin\left\{2;-2\right\}\)
b: Ta có: \(P=\left(\dfrac{2}{x+2}-\dfrac{4}{x^2+4x+4}\right):\left(\dfrac{2}{x^2-4}-\dfrac{1}{x-2}\right)\)
\(=\dfrac{2x+4-4}{\left(x+2\right)^2}:\dfrac{2-x-2}{\left(x-2\right)\left(x+2\right)}\)
\(=\dfrac{2x}{\left(x+2\right)^2}\cdot\dfrac{\left(x-2\right)\left(x+2\right)}{-x}\)
\(=\dfrac{-2\left(x-2\right)}{x+2}\)