Question

[Anna]

Tìm x biết 2mũx+1-3×2mũx-2=40

Answer 1

[Xyz OLM]

2^{x + 1} - 3.2^{x - 2} = 40 

<=> 2^{x - 2 + 3} - 3.2^{x - 2}  = 40

<=> 8.2^{x - 2} - 3.2^{x - 2} = 40

<=> 5.2^{x - 2} = 40

<=> 2^{x - 2}  = 8 

<=> 2^{x - 2} = 2³ 

<=> x - 2 = 3 

<=> x = 5

Answer 2

[Quỳnh Anh]

Trả lời:

2^{x + 1} - 3.2^{x - 2} = 40

<=> 2^x . 2 - 3 . 2^x : 2² = 40

<=> 2^x . 2 - 3 . 2^x : 4 = 40

<=> 2^x . 2 - 3 . 2^x . 1/4 = 40

<=> 2^x .( 2 - 3 . 1/4 ) = 40

<=> 2^x . 1,25 = 40

<=> 2^x = 32

<=> 2^x = 2⁵ 

=> x = 5