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

Toán Lớp 7: bài 10: cho a/b = c/d cmr h ac/bd = a ²+c ²/b ²+ d ²

Toán Lớp 7: bài 10: cho a/b = c/d cmr
h ac/bd = a ²+c ²/b ²+ d ²

Comments ( 2 )

  1. Giải đáp + giải thích các bước giải :  

    toan-lop-7-bai-10-cho-a-b-c-d-cmr-h-ac-bd-a-c-b-d

  2. $\\$
    Đặt a/b=c/d=k (k \ne 0)
    ->a=bk,c=dk
    (ac)/(bd)
    = (bk . dk)/(bd)
    = (bdk^2)/(bd)
    = k^2 (1)
    (a^2 +c^2)/(b^2 +d^2)
    = ( (bk)^2 + (dk)^2)/(b^2 +d^2)
    = (b^2k^2 +d^2k^2)/(b^2 +d^2)
    = (k^2 (b^2+d^2) )/(b^2 +d^2)
    = k^2 (2)
    Từ (1), (2)
    -> (ac)/(bd) = (a^2 +c^2)/(b^2 +d^2)(=k^2)

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