Question

Tìm số tự nhiên :

a, 2n - 28 = 2 2

b, 4n - 25 = 2x 4 2

c. 3n = 27 

d. n 4 - 1 = 80

Chú ý : đây là dạng toán Lũy Thừa 

Answer 1

a, \(2^n-28=2^2\)

\(\Rightarrow2^n-28=4\)

\(\Rightarrow2^n=4+28\)

\(\Rightarrow2^n=32\)

\(\Rightarrow2^n=2^5\)

\(\Rightarrow n=5\)

b, \(4^n-24=2\times4^2\)

\(\Rightarrow4^n-24=2\times16\)

\(\Rightarrow4^n-24=32\)

\(\Rightarrow4^n=32+24\)

\(\Rightarrow4^n=56\)

\(\Rightarrow4^n=4^4\)

\(\Rightarrow n=4\)

c,\(3^n=27\)

\(\Rightarrow3^n=3^3\)

\(\Rightarrow x=3\)

d, \(n^4+1=80\)

\(\Rightarrow n^4=80+1\)

\(\Rightarrow n^4=81\)

\(\Rightarrow n^4=3^4\)

\(\Rightarrow n=3\)

Answer 2

Cảm ơn nhiều !