Tìm x a)5^x.5^3=125^2.25^3 b)(-1/4)^x-2=1/64 c) (x-3/4)^2=49/81

Question

Tìm x a)5^x.5^3=125^2.25^3
b)(-1/4)^x-2=1/64
c) (x-3/4)^2=49/81

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Khải Quang 4 years 2020-10-16T06:12:31+00:00 2 Answers 110 views 0

Answers ( )

  1. minhkhoi
    0
    2020-10-16T06:13:38+00:00
    Reply

    Đáp án:

    a) $5^{x}$ . $5^{3}$ = $125^{2}$ . $25^{3}$

        $5^{x}$ . $5^{3}$ = 244140625 = $5^{12}$ 

             x                      = $5^{12}$ : $5^{3}$ = $5^{12 – 3}$ = $5^{4}$

             x                      = 4

  2. Farah
    0
    2020-10-16T06:13:38+00:00
    Reply

    Đáp án:

    `a)`

    ` 5^(x) * 5^3 = 125^2 * 25^3`

    ` => 5^(x) * 5^3 = (5^3)^2 * (5^2)^3`

    ` => 5^(x+3) = 5^6 * 5^6  = 5^12`

    ` => x +3 = 12`

    ` => x= 9` 

    `b)`

    ` (-1/4)^(x-2) = 1/64 = (-1/4)^4` 

    ` => x-2 = 4`

    ` => x= 6`

    `c)`

    ` (x-3/4)^2 = 49/81 = (7/9)^2 = -7/9`

    TH1

    ` x-3/4 = 7/9`

    ` => x= 7/9 +3/4 = 55/36`

    TH2

    ` x-3/4 = -7/9`

    ` => x= -7/9 +3/4`

    ` => x= -1/36`

    Vậy ` x= 55/36` hoặc ` x=-1/36`

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