Question

Tìm n ϵ N* biết :

a. ( 2² : 4 ).2ⁿ = 4

b. 2.16 ≥ 2ⁿ > 4 

Answer 1

a.(2^2 : 4) . 2^n = 4

=>(4:4) . 2^n = 4

=>2^n = 4

=>2^n = 2^2

=>n=2

b.2.16 >_ 2^n > 4

=>32 >_ 2^n > 2^2

=>2^5 >_ 2^n > 2^2

=>n={3;4;5}

Answer 2

\(a,\left(2^2:4\right)\cdot2^n=4\\ \Leftrightarrow2^n=2^2\\ \Leftrightarrow n=2\)

\(b,2\cdot16\ge2^n>4\\ \Leftrightarrow2^5\ge2^n>2^2\\ \Rightarrow2< n\le5\\ \Leftrightarrow n\in\left\{3;4;5\right\}\)