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

Toán Lớp 7: cho a.d=b.c chứng tỏ 3a+4b/5a+6b = 3c + 4d/ 5c+6d

Toán Lớp 7: cho a.d=b.c chứng tỏ 3a+4b/5a+6b = 3c + 4d/ 5c+6d

Comments ( 1 )

  1. Giải đáp:
     Lời giải và giải thích chi tiết:
     Có ad=bc⇒a/b=c/d=k
    ⇒a=bk,c=dk
    Xét \frac{3a+4b}{5a+6b}=\frac{3bk+4b}{5bk+6b}=\frac{b(3k+4)}{b(5k+6)}=\frac{3k+4}{5k+6}(1)
          \frac{3c+4d}{5c+6d}=\frac{3dk+4d}{5dk+6d}=\frac{d(3k+4)}{d(5k+6)}=\frac{3k+4}{5k+6}(2)
    Do đó \frac{3a+4b}{5a+6b}=\frac{3c+4d}{5c+6d}(đpcm)

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

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