`3^n = 81`
`3^n = 3^4`
`=> n=4`
____________________
`5^2 = 625`
`n = ?`
_______________________
\(6^{2n}=1296\)
\(6^{2n}=6^4\)
`=> 2n=4`
`n=4:2`
`n=2`
______________________
\(7^{n-1}=343\)
\(7^{n-1}=7^3\)
`=> n-1=3`
`n=3+1`
`n=4`
_____________________
\(9^{n+2}=729\)
\(9^{n+2}=9^3\)
`=>n +2=3`
`n=3-2`
`n=1`
______________________
`n^2 = 169`
`n^2 = 13^2`
`=> n` \(=\left(\pm13\right)^2\)
_________________________
\(n^3=729\)
`n^3 = 9^3`
`=> n=9`
_________________________
\(\left(n-2\right)^4=256\)
\(\left(n-2\right)^4=\left(\pm4\right)^4\)
`@TH1:`
`n-2=4`
`n=4+2`
`n=6`
`@TH2:`
`n-2=-4`
`n=-4+2`
`n=-2`
___________________________
\(n^7=n\)
`n^7 - n=0`
`=> n.(n^6 - 1)=0`
`@TH1:`
`n=0`
`@TH2:`
`n^6 + 1=0`
`n^6 = 1`
`=> n`\(=\left(\pm1\right)^6\)
___________________________
`n^3 = n^5`
`n^3 . n^5 = 0`
`=> n = ` \(\left(\pm1\right)\)
hoặc `n=0`
a) 3^n = 81
3^n = 3⁴
n = 4
b) Sai đề
c) 6^2n = 1296
6^2n = 6⁴
2n = 4
n = 4 : 2
n = 2
d) 7^(n-1) = 243
7^(n-1) = 7³
n - 1 = 3
n = 3 + 1
n = 4
e) 9^(n+2) = 729
9^(n+2) = 9³
n + 2 = 3
n = 3 - 2
n = 1
g) n² = 169
n² = 13²
n = 13
h) n³ = 729
n³ = 9³
n = 9
i) (n - 2)⁴ = 256
(n - 2)⁴ = 4⁴
n - 2 = 4
n = 4 + 2
n = 6
k) n¹⁰ = 1^n
n¹⁰ = 1
n = 1
m) n⁷ = n
n⁷ - n = 0
n(n⁶ - 1) = 0
n = 0 hoặc n⁶ - 1 = 0
*) n⁶ - 1 = 0
n⁶ = 1
n = 1
Vậy n = 0; n = 1
n) n³ = n⁵
n⁵ - n³ = 0
n³(n² - 1) = 0
n³ = 0 hoặc n² - 1 = 0
*) n³ = 0
n = 0
*) n² - 1 = 0
n² = 1
n = 1
Vậy n = 0; n = 1
