Question

Please help with 15, 17 and 19

Answer 1

Given:

15. $\log_{\frac{1}{2}}\left(\dfrac{1}{2}\right)$

17. $\log_{\frac{3}{4}}\left(\dfrac{4}{3}\right)$

19. $2^{\log_2100}$

To find:

The values of the given logarithms by using the properties of logarithms.

Solution:

15. We have,

$\log_{\frac{1}{2}}\left(\dfrac{1}{2}\right)$

Using property of logarithms, we get

$\log_{\frac{1}{2}}\left(\dfrac{1}{2}\right)=1$         $[\because \log_aa=1]$

Therefore, the value of $\log_{\frac{1}{2}}\left(\dfrac{1}{2}\right)$ is 1.

17. We have,

$\log_{\frac{3}{4}}\left(\dfrac{4}{3}\right)$

Using properties of logarithms, we get

$\log_{\frac{3}{4}}\left(\dfrac{4}{3}\right)=-\log_{\frac{3}{4}}\left(\dfrac{3}{4}\right)$                    $[\because \log_a\dfrac{m}{n}=-\log_a\dfrac{n}{m}]$

$\log_{\frac{3}{4}}\left(\dfrac{4}{3}\right)=-1$                 $[\because \log_aa=1]$

Therefore, the value of $\log_{\frac{3}{4}}\left(\dfrac{4}{3}\right)$ is -1.

19. We have,

$2^{\log_2100}$

Using property of logarithms, we get

$2^{\log_2100}=100$          $[\because a^{\log_ax}=x]$

Therefore, the value of $2^{\log_2100}$ is 100.