Toán Lớp 8: B=( ($\frac{x+1}{1-x}$- $\frac{1-x}{1+x}$ $\frac{4x^{2}}{x{2}-1}$): $\frac{4x^{2}-4}{x^{2}-2x+1}$ Rút gọn

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1. Rút gọn:
   B= ($\dfrac{x+1}{1-x}$- $\dfrac{1-x}{1+x}$- $\dfrac{4x²}{x²-1}$) : $\dfrac{4x²-4}{x²-2x+1}$ 
     = ($\dfrac{-x-1}{x-1}$- $\dfrac{1-x}{x+1}$- $\dfrac{4x²}{(x-1)(x+1)}$) : $\dfrac{4(x²-1)}{(x-1)²}$
     =  $\dfrac{(-x-1)(x+1)-(1-x)(x-1)-4x²}{(x-1)(x+1)}$ : $\dfrac{4(x-1)(x+1)}{(x-1)²}$
     = $\dfrac{-x²-x-x-1-x+1+x²-x-4x²}{(x-1)(x+1)}$ : $\dfrac{4(x-1)(x+1)}{(x-1)²}$
     = $\dfrac{-4x²-4x}{(x-1)(x+1)}$ : $\dfrac{4(x-1)(x+1)}{(x-1)²}$
     = $\dfrac{-4x(x+1)}{(x-1)(x+1)}$ . $\dfrac{(x-1)²}{4(x-1)(x+1)}$
     = $\dfrac{x}{x+1}$ 

                    Chúc bạn học tốt^^

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