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

Toán Lớp 8: Rút gọn: `(2/(x-1) – 1/(x+1)). (x^2 -1)/(x^2 + 6x+9) + (x+1)/(2x+6)`

Toán Lớp 8: Rút gọn:
(2/(x-1) – 1/(x+1)). (x^2 -1)/(x^2 + 6x+9) + (x+1)/(2x+6)

Comments ( 2 )

  1. Giải đáp:
     1/2
    Lời giải và giải thích chi tiết:
    (2/(x-1)-1/(x+1)) . (x^2-1)/(x^2+6x+9) + (x+1)/(2x+6) (x \ne ±1, x \ne -3)
    =(2(x+1)-(x-1))/((x-1)(x+1)) . ((x-1)(x+1))/((x+3)^2) + (x+1)/(2(x+3))
    =(2x+2-x+1) . 1/((x+3)^2) + (x+1)/(2(x+3))
    =(x+3) . 1/((x+3)^2) + (x+1)/(2(x+3))
    =1/(x+3) + (x+1)/(2(x+3))
    =(2+x+1)/(2(x+3))
    =(3+x)/(2(x+3))
    =1/2

  2. Gửi bạn:
    $ĐKXĐ:x\neq±1,-3$
    $(\dfrac{2}{x-1}-\dfrac{1}{x+1}).\dfrac{x^2-1}{x^2+6x+9}+\dfrac{x+1}{2x+6}$ 
    $=(\dfrac{2(x+1)}{(x-1)(x+1)}-\dfrac{x-1}{(x+1)(x-1)}).\dfrac{x^2-1}{x^2+6x+9}+\dfrac{x+1}{2x+6}$ 
    $=(\dfrac{2x+2}{(x-1)(x+1)}-\dfrac{x-1}{(x+1)(x-1)}).\dfrac{x^2-1}{x^2+6x+9}+\dfrac{x+1}{2x+6}$ 
    $=(\dfrac{2x+2-x+1}{(x-1)(x+1)}).\dfrac{x^2-1}{x^2+6x+9}+\dfrac{x+1}{2x+6}$ 
    $=\dfrac{1}{x+3}+\dfrac{x+1}{2(x+3)}$ 
    $=\dfrac{2}{2(x+3)}+\dfrac{x+1}{2(x+3)}$ 
    $=\dfrac{x+3}{2(x+3)}$ 
    $=\dfrac{1}{2}$ 
     

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

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