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

Toán Lớp 9: cho B= √x /√x-2 + 4√x /4-x – 2/√x+2 (x>0 , x khác 4) chứng minh B= √x-2/ √x+2

Toán Lớp 9: cho B= √x /√x-2 + 4√x /4-x – 2/√x+2 (x>0 , x khác 4)
chứng minh B= √x-2/ √x+2

Comments ( 2 )

  1. Giải đáp + giải thích :

    toan-lop-9-cho-b-2-4-4-2-2-0-khac-4-chung-minh-b-2-2

    B=\sqrtx/(\sqrtx-2)+(4\sqrtx)/(4-x)-2/(\sqrtx+2)(x>=0;xne4)

    =\sqrtx/(\sqrtx-2)-(4\sqrtx)/(x-4)-2/(\sqrtx+2)

    =(\sqrtx(\sqrtx+2)-4\sqrtx-2(\sqrtx-2))/((\sqrtx-2)(\sqrtx+2))

    =(x+2\sqrtx-4\sqrtx-2\sqrtx+4)/((\sqrtx-2)(\sqrtx+2))

    =(x-4\sqrtx+4)/((\sqrtx-2)(\sqrtx+2))

    =(\sqrtx-2)^2/((\sqrtx-2)(\sqrtx+2))

    =(\sqrtx-2)/(\sqrtx+2)(đfcm)

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