a:
ĐKXĐ: \(x\notin\left\{1;-1;2\right\}\)
\(\dfrac{2x-4}{x^2-1}\cdot\dfrac{x^3-3x^2+3x-1}{x-2}\)
\(=\dfrac{2\left(x-2\right)}{\left(x-1\right)\left(x+1\right)}\cdot\dfrac{\left(x-1\right)^3}{x-2}\)
\(=\dfrac{2\left(x-1\right)^2}{x+1}\)
b:
ĐKXĐ: \(x\notin\left\{2;3;1\right\}\)
\(\dfrac{x^2-3x+2}{x^2-5x+6}\cdot\dfrac{x^2-x-6}{x^2-2x+1}\)
\(=\dfrac{\left(x-2\right)\left(x-1\right)}{\left(x-2\right)\left(x-3\right)}\cdot\dfrac{\left(x-3\right)\left(x+2\right)}{\left(x-1\right)^2}\)
\(=\dfrac{x-1}{x-3}\cdot\dfrac{\left(x-3\right)\left(x+2\right)}{\left(x-1\right)^2}\)
\(=\dfrac{x-1}{\left(x-1\right)^2}\cdot\left(x+2\right)=\dfrac{x+2}{x-1}\)
