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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 8: $\frac{2}{x-1}$ + $\frac{-4}{ x^{2} -1 }$

Toán Lớp 8: $\frac{2}{x-1}$ + $\frac{-4}{ x^{2} -1 }$

Comments ( 2 )

  1. Giải đáp:
     
    Lời giải và giải thích chi tiết:
      2/[x-1] + [-4]/[x^2 -1] = 2/[x-1] – 4/[(x-1)(x+1)] = [2(x+1)]/[(x-1)(x+1)] – 4/[(x-1)(x+1)] = [2x+2-4]/[(x-1)(x+1)] = [2x-2]/[(x-1)(x+1)] = [2(x-1)]/[(x-1)(x+1)] = 2/[x+1]
    (Bài tham khảo)

  2. $\dfrac{2}{x-1}$ + $\dfrac{-4}{x^2-1}$
    = $\dfrac{2}{x-1}$ + $\dfrac{-4}{(x+1)(x-1)}$
    = $\dfrac{2.(x+1)}{(x-1)(x+1)}$ + $\dfrac{-4}{(x+1)(x-1)}$
    = $\dfrac{2.(x+1)-4}{(x-1)(x+1)}$ 
    = $\dfrac{2x+2-4}{(x-1)(x+1)}$ 
    = $\dfrac{2x-4}{(x-1)(x+1)}$ 
    = $\dfrac{2(x-1)}{(x-1)(x+1)}$ 
    = $\dfrac{2}{(x+1)}$ 

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222-9+11+12:2*14+14 = ? ( )