Question

Tìm x thuộc N biết :

a) 2^x . 4 = 128

b) 2^x = 4 . 128

c) 3^x = 3^3 . 3^5

d) 2^x . ( 2^2 ) mũ 3 = ( 2^3 ) mũ 2

Answer 1

\(a,2^x.4=128\)

\(\Leftrightarrow2^x=128:4\)

\(\Leftrightarrow2^x=32\)

\(\Leftrightarrow2^x=2^5\)

\(\Rightarrow x=5\)

\(b,2^x=4.128\)

\(\Leftrightarrow2^x=2^2.2^7\)

\(\Leftrightarrow2^x=2^9\)

\(\Rightarrow x=9\)

\(c,3^x=3^3.3^5\)

\(\Leftrightarrow3^x=3^8\)

\(\Rightarrow x=8\)

\(d,2^x.\left(2^2\right)^3=\left(2^3\right)^2\)

\(\Leftrightarrow2^x.2^6=2^6\)

\(\Leftrightarrow2^x=2^6:2^6\)

\(\Leftrightarrow2^x=1\)

\(\Rightarrow x=0\)

Answer 2

Trả lời:

a, 2^x . 4 = 128

=> 2^x = 32

=> 2^x = 2⁵

=> x = 5

b, 2^x = 4.128

=> 2^x = 512

=> 2^x = 2⁹

=> x = 9

c, 3^x = 3³ . 3⁵ 

=> 3^x = 3⁸

=> x = 8

d, 2^x ( 2² )³ = ( 2³ )²

=> 2^x . 2⁶ = 2⁶

=> 2^x = 1

=> 2^x = 2⁰

=> x = 0