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

Toán Lớp 7: cho a/b=c/d, chứng minh : (2a+3b)(4c-5d)= (4a-5b)(2c+3d)

Toán Lớp 7: cho a/b=c/d, chứng minh : (2a+3b)(4c-5d)= (4a-5b)(2c+3d)

Comments ( 1 )

  1. Vì a/b=c/d
    (2a+3b)(4c-5d)= (4a-5b)(2c+3d)
    <=> 8ac – 10ad + 12bc -15bd = 8ac + 12ad – 10bc -15bd
    <=> -10ad + 12bc = 12ad – 10bc
    <=> (-10ad+12bc)+(-12bc-12ad)=(12ad-10bc)+(-12bc-12ad)
    <=> 22bc = 22ad
    => TMDK

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