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avatar+22 

How to solve 2^-log5(base 2) without a calculator? Thanks.

 Mar 17, 2016

Best Answer 

 #2
avatar+128707 
+10

I assume you have this :

 

2^(-log2 5)   if so.....we can write this as

 

2^(log2 5-1)  =

 

2^[log2 (1/5) ]  =

 

1/5

 

This goes back to the property that says  that  ...   b^(logb a)  = a      where b is a positive base

 

 

 

cool cool cool

 Mar 17, 2016
 #1
avatar+1491 
0

Go for it CP, logs are not my thing.

 Mar 17, 2016
 #2
avatar+128707 
+10
Best Answer

I assume you have this :

 

2^(-log2 5)   if so.....we can write this as

 

2^(log2 5-1)  =

 

2^[log2 (1/5) ]  =

 

1/5

 

This goes back to the property that says  that  ...   b^(logb a)  = a      where b is a positive base

 

 

 

cool cool cool

CPhill Mar 17, 2016
 #3
avatar+1904 
0

How did you get \({5}^{-1}\)?

gibsonj338  Mar 17, 2016
 #4
avatar+128707 
0

Look at this, gibson338...

 

-log2 5  =  (-1) log2 5      and by a property of logs, we have

 

a log b   =  log ba     ...... so......

 

(-1)log2 5     becomes   log2 5-1     and 5-1   = 1/5

 

So   we end up with     2^ [log2 1/5]

 

 

 

cool cool cool

 Mar 17, 2016
 #5
avatar+1904 
0

I get you now.  I did not see the "-" in front of the log.

gibsonj338  Mar 17, 2016

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