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

Toán Lớp 6: Tìm x : (17x – 25): 8 + 65 = 9^2 25< 5^x< 3125 2^x: 4 = 16

Toán Lớp 6: Tìm x :
(17x – 25): 8 + 65 = 9^2
25< 5^x< 3125 2^x: 4 = 16

Comments ( 2 )

  1. a)(17x – 25) : 8 + 65 = $9^{2}$ 
    (17x – 25 ) : 8 + 65 = 81
    (17x – 25 ) : 8         = 81 – 65
    (17x – 25 ) : 8         = 16
    17x – 25                 = 16 . 8 = 128
    17x                        = 128 + 25 = 153
    x                            = 152 : 17 = 9
    b) 25 < 5x < 3125
    →$5^{2}$ < $5^{x}$ < $5^{5}$
      ⇒ 2 < x < 5
    Mà x ∈ Z
    ⇒ x = 4 ; 3
    c) $2^{x}$ : 4 = 16
        $2^{x}$      = 16 x 4 = 64
        $2^{x}$      = $2^{6}$ 
               x          = 6
      
     

  2. $#Peter$
    (17x – 25): 8 + 65 = 9^2
    (17x – 25): 8 + 65 = 81
    (17x – 25): 8 = 81 – 65
    (17x – 25): 8 = 16
    17x – 25 = 16.8
    17x – 25 = 128
    17x = 128 + 25
    17x = 153
    x=153:17
    x = 9
    Vậy x=9
    25< 5x< 3125
    5^2< 5x< 5^5
    => 2 < x < 5
    =>x=3 hoặc x=4
    Vậy x=3 hoặc x=4
    2^x: 4 = 16
    2^x= 16 × 42
    x= 64
    2^x= 2^6
    => x = 6
    Vậy x=6

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