Question

Tìm x thuộc N biết :

16^x < 128⁴

Answer 1

16^x < 128⁴ 
=> (4²)^x < 128⁴
=> 4^2x< 128⁴
=> (2²)^2x < 128⁴
=> 2^4x < (2⁷)⁴
=> 2^4x < 2²⁸
=> 4x < 28 
=> x < 7 
vậy x = {0,1,2,3,4,5,6} 

Answer 2

16^x = (2⁴)^x = 2^4x

128⁴ = (2⁷)⁴ = 2²⁸

2^4x > 2²⁸ 

=> 4x < 28

=> x = {1,2,3,4,5,6}