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

Toán Lớp 8: 4/x+1 + 4/x-1 – x^2+7/x^2-1

Home/ Toán Lớp 8: 4/x+1 + 4/x-1 – x^2+7/x^2-1

Toán Lớp 8: 4/x+1 + 4/x-1 – x^2+7/x^2-1

Tháng Sáu 21, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: 4/x+1 + 4/x-1 – x^2+7/x^2-1

Comments ( 2 )

  1. huongtructram
    huongtructram
    21 Tháng Sáu, 2022 at 8:27 sáng
    Reply
    Answer
    4/{x + 1} + 4/{x – 1} – {x^{2} + 7}/{x^{2} – 1}
    = 4/{x + 1} + 4/{x – 1} – {x^{2} + 7}/{x^{2} – 1^{2}}
    = 4/{x + 1} + 4/{x – 1} – {x^{2} + 7}/{(x – 1) . (x + 1)}
    = {4 . (x – 1)}/{(x + 1) . (x – 1)} + {4 . (x + 1)}/{(x – 1) . (x + 1)} – {x^{2} + 7}/{(x – 1) . (x + 1)}
    = {4x – 4}/{(x + 1) . (x – 1)} + {4x + 4}/{(x – 1) . (x + 1)} – {x^{2} + 7}/{(x – 1) . (x + 1)}
    = {(4x – 4) + (4x + 4) – (x^{2} + 7)}/{(x – 1) . (x + 1)}
    = {4x – 4 + 4x + 4 – x^{2} – 7}/{(x – 1) . (x + 1)}
    = {(4x + 4x) + (4 – 4 – 7) – x^{2}}/{(x – 1) . (x + 1)}
    = {8x – 7 – x^{2}}/{(x – 1) . (x + 1)}
    = {-x^{2} + 8x – 7}/{(x – 1) . (x + 1)}
    = {(x – 1) . (7 – x)}/{(x – 1) . (x + 1)}
    = {7 – x}/{x + 1}

  2. dongoclandiem
    dongoclandiem
    21 Tháng Sáu, 2022 at 8:27 sáng
    Reply
    @Bao
    4/(x+1)+4/(x-1)-(x^2+7)/(x^2-1)
    =4/(x+1)+4/(x-1)-(x^2+7)/((x-1)(x+1))
    =(4(x-1))/((x-1)(x+1))+(4(x+1))/((x-1)(x+1))-(x^2+7)/((x-1)(x+1))
    =(4(x-1)+4(x+1)-x^2-7)/((x-1)(x+1))
    =(4x-4+4x+4-x^2-7)/((x-1)(x+1))
    =(8x-x^2-7)/((x-1)(x+1))
    =((x-1)(7-x))/((x-1)(x+1))
    =(7-x)/(x+1)

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

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