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

Toán Lớp 7: a.d=b.d chứng minh 2a-b/a+3b = 2c-d/c+3d

Toán Lớp 7: a.d=b.d chứng minh 2a-b/a+3b = 2c-d/c+3d

Comments ( 2 )

  1. $\\$
    Có : ad=bc
    -> a/b=c/d
    Đặt a/b=c/d=k (k \ne 0)
    ->a/b=k->a=bk
    và c/d=k->c=dk
    Có : (2a-b)/(a+3b)
    = (2bk – b)/(bk +3b)
    = (b (2k-1) )/(b (k+3) )
    = (2k-1)/(k+3) (1)
    Có : (2c-d)/(c+3d)
    = (2dk – d)/(dk + 3d)
    = (d (2k-1) )/(d (k+3) )
    = (2k-1)/(k+3) (2)
    Từ (1), (2)
    -> (2a-b)/(a+3b) = (2c-d)/(c+3d) (= (2k-1)/(k+3) )
    -> Điều phải chứng minh
     

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