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

Toán Lớp 7: Bài 1 Tìm x biết a, 2^x = 16 b,(x/13)^2 = 49/169 c,(-2/3)^x = -8/27 d,(-1/5)^x = (-1/125)^3 e, x^4 = -16/625 f, (3/4)^x = 2^8/3^4

Toán Lớp 7: Bài 1 Tìm x biết
a, 2^x = 16
b,(x/13)^2 = 49/169
c,(-2/3)^x = -8/27
d,(-1/5)^x = (-1/125)^3
e, x^4 = -16/625
f, (3/4)^x = 2^8/3^4

Comments ( 1 )

  1. a)2^x=16
    =>2^x=2^4
    =>x=4
    b)(x/13)^2=49/(169)
    =>(x/13)^2=(7/13)^2
    =>x/13=7/13
    =>x.13=7.13
    =>x=7.13:13
    =>x=7.1
    =>x=7
    c)(-2/3)^x=-8/27
    =>(-2/3)^x=(-2/3)^3
    =>x=3
    d)(-1/5)^x=(-1/125)^3
    =>(-1/5)^x=[(-1/5)^3]^3
    =>(-1/5)^x=(-1/5)^9
    =>x=9
    e)x^4=-16/625
    =>x^4=(-2/5)^4
    =>x=-2/5
    f)(3/4)^x=(2^8)/3^4
    =>(3/4)^x=(256)/81
    =>(3/4)^x=(4/3)^4
    =>(3/4)^x=(3/4)^(-4)
    =>x=-4
    Câu f mình không chắc chắc đúng lắm ạ.

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

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