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

Toán Lớp 8: Thực hiện phép tính A) x + 1/x-1 + x -1/x+1 – 4/x^2 -1 B) 5x + 1/ x-1 + 3x-2/x-1 C) x + 1/x -2 + 4/x+2 + 2 – 7x/x^2 – 4 Giúp em bới ặ

Tháng Sáu 7, 2022 Toán học 1 Comment 0 views

Toán Lớp 8: Thực hiện phép tính
A) x + 1/x-1 + x -1/x+1 – 4/x^2 -1
B) 5x + 1/ x-1 + 3x-2/x-1
C) x + 1/x -2 + 4/x+2 + 2 – 7x/x^2 – 4
Giúp em bới ặ

Comments ( 1 )

  1. bichhhathu
    bichhhathu
    7 Tháng Sáu, 2022 at 4:43 chiều
    Reply
    Giải đáp:
    a) $\dfrac{x+1}{x-1}+\dfrac{x-1}{x+1}-\dfrac{4}{x^2-1}=2$
    b) $\dfrac{5x+1}{x-1}+\dfrac{3x-2}{x-1}=\dfrac{8x-1}{x-1}$
    c) $\dfrac{x+1}{x-2}+\dfrac{4}{x+2}+\dfrac{2-7x}{x^2-4}=1$
    Lời giải và giải thích chi tiết:
    a)
    $\dfrac{x+1}{x-1}+\dfrac{x-1}{x+1}-\dfrac{4}{x^2-1}\,\,\,(x\ne\pm1)\\=\dfrac{x+1}{x-1}+\dfrac{x-1}{x+1}-\dfrac{4}{(x-1)(x+1)}\\=\dfrac{(x+1)^2+(x-1)^2-4}{(x-1)(x+1)}\\=\dfrac{x^2+2x+1+x^2-2x+1-4}{(x-1)(x+1)}\\=\dfrac{2x^2-2}{(x-1)(x+1)}\\=\dfrac{2(x-1)(x+1)}{(x-1)(x+1)}\\=2$
    b)
    $\dfrac{5x+1}{x-1}+\dfrac{3x-2}{x-1}\,\,\,(x\ne1)\\=\dfrac{5x+1+3x-2}{x-1}\\=\dfrac{8x-1}{x-1}$
    c)
    $\dfrac{x+1}{x-2}+\dfrac{4}{x+2}+\dfrac{2-7x}{x^2-4}\,\,\,(x\ne\pm2)\\=\dfrac{x+1}{x-2}+\dfrac{4}{x+2}+\dfrac{2-7x}{(x-2)(x+2)}\\=\dfrac{(x+1)(x+2)+4(x-2)+2-7x}{(x-2)(x+2)}\\=\dfrac{x^2+3x+2+4x-8+2-7x}{(x-2)(x+2)}\\=\dfrac{x^2-4}{(x-2)(x+2)}\\=\dfrac{(x-2)(x+2)}{(x-2)(x+2)}\\=1$

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

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