# Math Help - Change of base

1. ## 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

2. 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