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

Toán Lớp 7: xy+xz/2=yx+yz/3=zx+zy/4;cmr x/3=y/5=z/15 mn helppppppppppppppppppp

Tháng Hai 4, 2023 Toán học 1 Comment 0 views

Toán Lớp 7: xy+xz/2=yx+yz/3=zx+zy/4;cmr x/3=y/5=z/15
mn helppppppppppppppppppp

Comments ( 1 )

  1. lanngocha
    lanngocha
    4 Tháng Hai, 2023 at 8:38 sáng
    Reply
    Lời giải và giải thích chi tiết:
    Ta có:
    $\dfrac{xy+xz}2=\dfrac{yx+yz}{3}=\dfrac{zx+zy}4=\dfrac{(xy+xz)+(yx+yz)+(zx+zy)}{2+3+4}$
    $\to\dfrac{xy+xz}2=\dfrac{yx+yz}{3}=\dfrac{zx+zy}4=\dfrac{2(xy+yz+zx)}{9}$
    $\to\dfrac{xy+xz}2=\dfrac{yx+yz}{3}=\dfrac{zx+zy}4=\dfrac{xy+yz+zx}{4.5}$
    $\to \dfrac{xy+yz+zx-(xy+xz)}{4.5-2}=\dfrac{xy+yz+zx-(yx+yz)}{4.5-3}=\dfrac{xy+yz+zx-(zx+zy)}{4.5-4}$
    $\to \dfrac{yz}{2.5}=\dfrac{zx}{1.5}=\dfrac{xy}{0.5}$
    $\to \dfrac{xyz}{2.5x}=\dfrac{zxy}{1.5y}=\dfrac{xyz}{0.5z}$
    $\to 2.5x=1.5y=0.5z$
    $\to\dfrac{2.5x}{7.5}=\dfrac{1.5y}{7.5}=\dfrac{0.5z}{7.5}$
    $\to\dfrac{x}3=\dfrac{y}5=\dfrac{z}{15}$
    $\to đpcm$

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

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