a. ĐKXĐ: \(x\ne\left\{0;-1;1\right\}\)
\(\dfrac{1-x^2}{x^2+2x}:\dfrac{2-2x}{3x}=\dfrac{\left(1-x\right)\left(1+x\right)}{x\left(x+2\right)}:\dfrac{2\left(1-x\right)}{3x}\)
\(=\dfrac{\left(1-x\right)\left(1+x\right)}{x\left(x+2\right)}.\dfrac{3x}{2\left(1-x\right)}=\dfrac{3\left(1+x\right)}{2\left(x+2\right)}\)
b. ĐKXĐ: \(x\ne1\)
\(\dfrac{x^3+1}{x-1}:\left(x^2-x+1\right)=\dfrac{\left(x+1\right)\left(x^2-x+1\right)}{\left(x-1\right)\left(x^2-x+1\right)}\)
\(=\dfrac{x+1}{x-1}\)
c. ĐKXĐ: \(x\ne\left\{-2;-1;0;2\right\}\)
\(\dfrac{x^2-x-2}{x^2+3x+2}:\dfrac{x^2-4x+4}{x^2+2x}=\dfrac{\left(x+1\right)\left(x-2\right)}{\left(x+1\right)\left(x+2\right)}:\dfrac{\left(x-2\right)^2}{x\left(x+2\right)}\)
\(=\dfrac{x-2}{x+2}.\dfrac{x\left(x+2\right)}{\left(x-2\right)^2}=\dfrac{x}{x-2}\)
