Question

Tìm số nguyên n biết :

a)\(\left(2^2:4\right).2^n=32\)

b)\(27< 3^n< 243\)

c)\(125\le5.5^n\le25\)

Nhanh giúp mình nhé chiều mai kiểm tra rồi ....

Answer 1

a) \(\left(2^2:4\right).2^n=2=32\)

\(\Leftrightarrow\left(2^2:2^2\right).2^n=2^5\)

\(\Leftrightarrow2^{2-2}.2^n=2^5\)

\(\Leftrightarrow2^0.2^n=2^5\)

\(\Leftrightarrow1.2^n=2^5\)

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

\(\Leftrightarrow n=5\)

Vậy n=5

b) \(27< 3^n< 243\)

\(\Leftrightarrow3^3< 3^n< 3^5\)

\(\Leftrightarrow3< n< 5\)

\(\Rightarrow n=4\)

Vậy n=4

Answer 2

a. \(\left(2^2:4\right).2^n=32\)

\(\Rightarrow\left(4:4\right).2^n=32\)

\(\Rightarrow2.2^n=32\)

\(\Rightarrow2^n=32:1=32=2^5\)

\(\Rightarrow n=5\)

Vậy................

b. \(27< 3^n< 243\)

\(\Leftrightarrow3^3< 3^n< 3^5\)

\(\Rightarrow3< n< 5\)

\(\Rightarrow n=4\)

c. đề bài có j đó sai sai