# plus and minus logs

• Nov 3rd 2009, 07:55 PM
realistic
plus and minus logs
http://img62.imageshack.us/img62/9256/logs3.jpgi can do the first one but the second one i cant seem to work it out
• Nov 3rd 2009, 10:25 PM
mr fantastic
Quote:

Originally Posted by realistic
http://img62.imageshack.us/img62/9256/logs3.jpgi can do the first one but the second one i cant seem to work it out

What base are you working to? That is an important omission on your part. Note that, for a > 0, \$\displaystyle 1 = \log_{a} a\$ ....
• Nov 3rd 2009, 10:26 PM
realistic
Quote:

Originally Posted by mr fantastic
What base are you working to? That is an important omission on your part. Note that, for a > 0, \$\displaystyle 1 = \log_{a} a\$ ....

thats how the question in the book is

log3−log10+1

wouldnt the answer just be log3?
• Nov 3rd 2009, 10:28 PM
mr fantastic
Quote:

Originally Posted by realistic
thats how the question in the book is

Well, if the base is 10 then you know that \$\displaystyle \log 10 = 1\$ and so the answer to the second question is plainly \$\displaystyle \log 3\$ since the 1's will cancel.
• Nov 3rd 2009, 10:30 PM
realistic
Quote:

Originally Posted by mr fantastic
Well, if the base is 10 then you know that \$\displaystyle \log 10 = 1\$ and so the answer to the second question is plainly \$\displaystyle \log 3\$ since the 1's will cancel.

ah yeah i see that but was not sure thanks for explaining it out