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N=2

how do i get this?

2007-10-16 14:31:42 · 9 answers · asked by Anonymous in Science & Mathematics Mathematics

9 answers

3^(n + 2) = 81
n + 2 = 4
n = 2

PS
Use brackets to clarify question.
What you have in fact typed means:-
(3^n) + 2 = 81
i.e. a completely different question.

2007-10-17 22:05:00 · answer #1 · answered by Como 7 · 0 0

Hello,
3^(n+2) = 81 so 3^(n+2) = 3^4 so since the bases the exponents must be equal then n+2 = 4 so n = 2.

Hope This Helps!

2007-10-16 21:36:11 · answer #2 · answered by CipherMan 5 · 1 0

n = 2

4th root of 81 = 3

3^4 = 81

2007-10-16 21:35:42 · answer #3 · answered by Anonymous · 0 0

3^(n+2)=81 dont get confuse with 3^n+2=81

Your answer suggest we have 3^(n+2)=81 situation.

so it means 3 times how many it self will be 81?
3 = 3
3*3=9
3*3*3=27
3*3*3*3=81

Now you get 3^4 = 81
4=n+2
n=2

2007-10-16 21:37:53 · answer #4 · answered by john_lu66 4 · 1 0

oh, you mean 3^(n+2)=81 xD
To do this, you'll need to know some logarithm laws:
Log2(2^x)=x
Log3(3^x)=x
Log base 'x', x to the power of something always equals something
Sooo, you could do:
Log3(3^n+2)=Log3(81)
n+2=4
n=2

Another law is that Log(x)^y=yLog(x)
Sooo, you could also do Log(3^(n+2))=log(81)
(n+2)(Log(3))=Log(81)
N+2=Log(81)/Log(3)
n=(Log(81)/Log(3))-2
n=2

The last way is to just think of exponentials
3^(n+2)=81, 81=3^4
3^(n+2)=3^4, get rid of the bases, since they are the same
n+2=4
n=2

2007-10-16 21:39:15 · answer #5 · answered by Chaotic_Shadow 3 · 0 0

I assume you meant

3^(n+2)=81 not 3^n +2 =81

3^(n+2) = 3^n (3^2) =81
3^n = 9

3^2 =9 , hence n =2

To avoid any confusion, please use parentheses to make it easy for all

2007-10-16 21:39:39 · answer #6 · answered by Any day 6 · 0 0

n does not equal 2
3^2 +2= 11

get to 3^n=79
now do ln3^n=ln79
ln is the natural log on calculator
n=ln79/ln3
n=3.977242834

2007-10-16 21:37:06 · answer #7 · answered by Anonymous · 0 0

3^n+2 = 81
3^n = 79
ln(3^n) = ln(79)
(n)ln(3) = ln(79)
n = ln(79)/ln(3)

or is it 3^(n+2)?
if this is the case, you know that 3^4 = 81. so if you set up the equation like this:
n+2 = 4
n=2.

2007-10-16 21:36:13 · answer #8 · answered by seaniquanzo 2 · 1 0

3x3=9x3=27x3=81
this is 3^4
s0 n=2

2007-10-16 21:36:02 · answer #9 · answered by science teacher 7 · 0 0

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