Question

Tìm số tự nhiên n, biết :

a)  7ⁿ =343:49                    b)  5ⁿ=625:25

Answer 1

a)7ⁿ=343:49

=>7ⁿ=7

=>7ⁿ=7¹

b)5ⁿ=625:25

=>5ⁿ=25

=>5ⁿ=5²

Answer 2

\(7^n=343:49=7^1\Rightarrow n=1\\ \)

\(5^n=625:25=25=5^2\Rightarrow n=2\)

Answer 3

343:49=7

\(\Rightarrow\)n=1

625:25=25

\(\Rightarrow\)n=2

Answer 4

a, \(7^n=343:49\)

\(\Rightarrow7^n=7^3:7^2\)

\(\Rightarrow7^n=7^1\)

\(\Rightarrow n=1\)

Vậy \(n=1\)

b, \(5^n=625:25\)

\(\Rightarrow5^n=5^4:5^2\)

\(\Rightarrow5^n=5^2\)

\(\Rightarrow n=2\)

Vậy \(n=2\)