a) \(A=\dfrac{x-2}{x}=\dfrac{\dfrac{2}{3}-2}{\dfrac{2}{3}}\)\(=-2\)
b)\(B=\dfrac{4x}{x+1}+\dfrac{x}{1-x}+\dfrac{2x}{x^2-1}\left(ĐK:x\ne\pm1\right)\)
\(=\dfrac{4x\left(x-1\right)}{\left(x+1\right)\left(x-1\right)}-\dfrac{x\left(x+1\right)}{\left(x-1\right)\left(x+1\right)}+\dfrac{2x}{\left(x-1\right)\left(x+1\right)}\)
\(=\dfrac{4x\left(x-1\right)-x\left(x+1\right)+2x}{\left(x-1\right)\left(x+1\right)}\)
\(=\dfrac{4x^2-4x-x^2-x+2x}{\left(x-1\right)\left(x+1\right)}\)\(=\dfrac{3x^2-3x}{\left(x-1\right)\left(x+1\right)}=\dfrac{3x\left(x-1\right)}{\left(x-1\right)\left(x+1\right)}=\dfrac{3x}{x+1}\)