# Change of base

• September 12th 2007, 12:44 AM
bungy189
Change of base
Hi,

If anyone can help pls

The formula for change of base is logbz = 1/ log z b

Use this formula to solve logz5 + log5Z =2

thank you
• September 12th 2007, 01:02 AM
Jhevon
Quote:

Originally Posted by bungy189
Hi,

If anyone can help pls

The formula for change of base is logbz = 1/ log z b

Use this formula to solve logz5 + log5Z =2

thank you

i don't see your problem here. you were given the formula to use

$\log_z 5 + \log_5 z = 2$

$\Rightarrow \frac {1}{\log_5 z} + \log_5 z = 2$

$\Rightarrow \left( \log_5 z \right)^2 - 2 \log_5 z + 1 = 0$

the above is quadratic in $\log_5 z$. now continue