Question 2172: please please please what is
logx81=4
Found 2 solutions by vms, khwang:
Answer by vms(2)   (Show Source):
You can put this solution on YOUR website! logx81=4
we know logxa=k if a= x^k
that means ...
if 'a' can be written as k th power of x then we say k is logarithm of a to base x.
as we see 3 = 3^1
9=3^2
27=3^3
81=3^4
which shows 81 can be got as 4th power of 3. so, logx81=4 implies x=3
Answer by khwang(438) (Show Source):
You can put this solution on YOUR website! Use loga b = 1/logb a,we have
logx 81= 4 converts to
1/log81 x = 4,
or log81 x = 1/4,
Hence, x = (81)^1/4 by definition of logarithm.
So, x = (81)^1/4 = (3^4)^(1/4) = 3^1 = 3.
Or use logx 81= log 81/log x = 4, (common logarithm:base 10)
So,log x = (log 81)/4,
x = 10^((log 81)/4) = 10^((log 3^4)/4) = 10^(4(log 3)/4)
= 10^(log 3) = 3
Kenny
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