Question

Tìm x thuộc N

a)2^x(2 mũ x):4=128

b)x^15(x mũ 15)=x

c)(2.x+1)^3(mũ 3)=125

Answer 1

a) 2^x : 4 = 128

=> 2x  = 512

=> 2^x  = 2⁹

=> x = 9

b) x¹⁵ = x

=> x¹⁵  = x¹⁵

=> x = 1 hoặc 0

c) ( 2x + 1 )³ = 125

=> ( 2x + 1 )³ = 5³

=> 2x + 1 = 5

=> 2x = 4

=> x = 2

Answer 2

a) 2^x : 4 = 128

=> 2^x = 128 . 4

=> 2^x = 512

=> 2^x = 2⁹

=> x = 9

b) x¹⁵ = x

=> x¹⁵ = x¹⁵

=> x = 1 hoặc 0

c) ( 2x + 1 )³ = 125

=> ( 2x + 1 )³ = 5³

=> 2x + 1 = 5

=> 2x = 5 - 1

=> 2x = 4

=> x = 4 : 2

=> x = 2