# Need help with Log please

• Dec 5th 2008, 12:06 PM
Jenne
Hi I am having a hard time understanding logs in class can someone help?

1.
I am to find the exact value for this
How would I start

2^log base2 7

Am i to transform this somehow first?

2.Another one is logbase6 6^74 for this one I got a 74 it is right but why? its juse the exponent of the 6
• Dec 5th 2008, 12:41 PM
running-gag
Quote:

Originally Posted by Jenne
Hi I am having a hard time understanding logs in class can someone help?

1.
I am to find the exact value for this
How would I start

2^log base2 7

Am i to transform this somehow first?

2.Another one is logbase6 6^74 for this one I got a 74 it is right but why? its juse the exponent of the 6

$log_2 7$ is the real x such as $2^x = 7$
Therefore $2^{log_2 7} = 7$

In the same way
$log_6 {6^{74}}$ is the real x such as $6^x = 6^{74}$
Therefore $log_6 {6^{74}} = 74$
• Dec 5th 2008, 12:48 PM
masters
Quote:

Originally Posted by Jenne
Hi I am having a hard time understanding logs in class can someone help?

1.
I am to find the exact value for this
How would I start

2^log base2 7

Am i to transform this somehow first?

$b^{\log_bx}=x$

$2^{\log_27}=7$

Quote:

Originally Posted by Jenne
2.Another one is logbase6 6^74 for this one I got a 74 it is right but why? its juse the exponent of the 6

$\log_b b^x=x$

$\log_6 6^{74}=74$

Just some more properties of logarithms. See here: Logarithmic Properties
Enjoy.