\(c,Sửa:\dfrac{1}{4x+2}=\dfrac{x\left(2x-1\right)}{2x\left(2x+1\right)\left(2x-1\right)}\\ \dfrac{20}{4x^3-x}=\dfrac{40}{2x\left(2x+1\right)\left(2x-1\right)}\\ \dfrac{7}{2x^2+x}=\dfrac{7\left(2x-1\right)}{x\left(2x+1\right)\left(2x-1\right)}\\ d,\dfrac{x}{x-y};\dfrac{x^2-y^2}{x^2-2xy+y^2}=\dfrac{\left(x-y\right)\left(x+y\right)}{\left(x-y\right)^2}=\dfrac{x+y}{x-y};x+y=\dfrac{x^2-y^2}{x-y}\\ e,\dfrac{x}{x+1}=\dfrac{x\left(x-1\right)}{\left(x-1\right)\left(x+1\right)};\dfrac{x^2}{1-x}=\dfrac{-x^2\left(x+1\right)}{\left(x+1\right)\left(x-1\right)};\dfrac{1}{x^2-1}=\dfrac{1}{\left(x-1\right)\left(x+1\right)}\)