a: \(=\dfrac{4x^2+4x+1-4x^2+4x-1}{\left(2x-1\right)\left(2x+1\right)}\cdot\dfrac{5\left(2x-1\right)}{4x}\)
\(=\dfrac{8x\cdot5}{4x\left(2x+1\right)}=\dfrac{10}{2x+1}\)
b: \(=\dfrac{1-2x+x^2}{x\left(x+1\right)}:\dfrac{x^2-2x+1}{x}\)
\(=\dfrac{x}{x\left(x+1\right)}=\dfrac{1}{x+1}\)


