Question

9ⁿ-¹=81

Answer 1

9^n-1=81=9²

=>n-1=2

=>n=3

Answer 2

\(9^{n-1}=81\Rightarrow3^{2n-2}=81\)

=> \(3^{2n-2}=3^4\)  (vì 81 = 3⁴)

=> \(2n-2=4\Rightarrow2n=6\Rightarrow n=\frac{6}{2}=3\)