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

Toán Lớp 7: Cho 4^x : 2^x+y=8 9^x+y : 3^5y Tìm x.y

Toán Lớp 7: Cho 4^x : 2^x+y=8
9^x+y : 3^5y
Tìm x.y

Comments ( 1 )

  1. 4^x=8 suy ra 2^2x/ 2^x+y=2^3
    suy ra 2^2x-x-y=2^3suy ra x-y=3(1)
    9^x+y/3^5y=243 suy ra 3^2x+2y/3^5y=3^5
    suy ra 3^2x+2y-5y=3^5 suy ra 2x-3y=5(2)
    Từ (1) và (2) ta có hpt:
    {x-y=3                                     x=4
    {2x-3y=5                      suy ra y=1
    vậy x=4, y=1

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

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