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

Toán Lớp 6: Tìm số tự nhiên x, biết: 1) 7^x+1= 49 2) 5^x-1= 25 3) 2^x-1= 8 4) 2^x-1= 16 5) 2^x-2= 1

Toán Lớp 6: Tìm số tự nhiên x, biết:
1) 7^x+1= 49
2) 5^x-1= 25
3) 2^x-1= 8
4) 2^x-1= 16
5) 2^x-2= 1

Comments ( 2 )

  1. 1) 7^x+1= 49=7²
    x+1=2
    x=2-1=1
    2) 5^x-1= 25=5²
    x-1=2
    x=2+1=3
    3) 2^x-1= 8=2³
    x-1=3
    x=3+1=4
    4) 2^x-1= 16=2^4
    x-1=4
    x=4+1=5
    5) 2^x-2= 1=2^0
    x-2=0
    x=0+2=2
    @Vinh2010

  2. 1)7^{x+1}=49
    7^{x+1}=7²
    ⇒x+1=7
    ⇒x=7-1
    ⇒x=6
    2)5^{x-1}=25
    ⇒5^{x-1}=5²
    ⇒x-1=2
    ⇒x=2+1
    ⇒x=3
    3)2^{x-1}=8
    ⇒2^{x-1}=2³
    ⇒x-1=3
    ⇒x=3+1
    ⇒x=4
    4)2^{x-1}=16
    ⇒2^{x-1}=$2^4$
    ⇒x-1=4
    ⇒x=4+1
    ⇒x=5
    5)2^{x-2}=1
    ⇒2^{x-2}=$2^0$
    ⇒x-2=0
    ⇒x=0+2
    ⇒x=2
     

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