b:
ĐKXĐ: \(x\notin\left\{0;2;-2\right\}\)
\(\left(\dfrac{4}{x^3-4x}+\dfrac{1}{x+2}\right):\left(\dfrac{x-2}{x^2+2x}-\dfrac{x}{2x+4}\right)\)
\(=\left(\dfrac{4}{x\left(x-2\right)\left(x+2\right)}+\dfrac{1}{x+2}\right):\left(\dfrac{x-2}{x\left(x+2\right)}-\dfrac{x}{2\left(x+2\right)}\right)\)
\(=\dfrac{4+x\left(x-2\right)}{x\left(x-2\right)\cdot\left(x+2\right)}:\dfrac{2\left(x-2\right)-x^2}{x\left(x+2\right)\cdot2}\)
\(=\dfrac{x^2-2x+4}{x\left(x-2\right)\left(x+2\right)}\cdot\dfrac{2x\left(x+2\right)}{-\left(x^2-2x+4\right)}\)
\(=\dfrac{-2}{x-2}\)
c:ĐKXĐ: x<>0
\(\left(x-\dfrac{3}{x}\right):\left(\dfrac{x^2+2x+1}{x}-\dfrac{2x+4}{x}\right)\)
\(=\dfrac{x^2-3}{x}:\dfrac{x^2+2x+1-2x-4}{x}\)
\(=\dfrac{x^2-3}{x}\cdot\dfrac{x}{x^2-3}\)
=1
