# logarithmic function

• Sep 27th 2009, 12:04 PM
tyonna
logarithmic function
y=log_10x, is the ____ of the exponential function, y=10x. is ____ a reciprocal, inverse, direct variation, or ratio?

&

in a table were y varies inversely as x. how would you write an equation showing this variation?
x | 3 | 6 | 18
y | 3 | 3/2 | 1/2
• Sep 27th 2009, 12:36 PM
skeeter
Quote:

Originally Posted by tyonna
y=log_10x, is the ____ of the exponential function, y=10x. is ____ a reciprocal, inverse, direct variation, or ratio?

$\displaystyle log_{10}(100) = 2$

$\displaystyle 10^2 = 100$

what's happening?

&

in a table were y varies inversely as x. how would you write an equation showing this variation?
x | 3 | 6 | 18
y | 3 | 3/2 | 1/2

the bold statement above translates to ... $\displaystyle y = \frac{k}{x}$ ... where k is a constant.

...
• Sep 27th 2009, 03:42 PM
A Beautiful Mind
$\displaystyle y = kx$ stands for direct variation. $\displaystyle y = 10x$. Direct variation.
• Sep 27th 2009, 03:45 PM
Defunkt
Quote:

Originally Posted by A Beautiful Mind
$\displaystyle y = kx$ stands for direct variation. y= 10x. Direct variation.

The question is supposed to be $\displaystyle y = log_{10}x$ is the ________ of the exponential function, $\displaystyle y = 10^x$
• Sep 27th 2009, 03:57 PM
tyonna
Quote:

Originally Posted by Defunkt
The question is supposed to be $\displaystyle y = log_{10}x$ is the ________ of the exponential function, $\displaystyle y = 10^x$

that's what i was trying to write i just don't know how to on a computer
• Sep 27th 2009, 08:13 PM
pacman
1) http://www.mathhelpforum.com/math-he...7420d4f4-1.gif is the logarithmic form of the exponential function, http://www.mathhelpforum.com/math-he...a59acc06-1.gif.

2) y= k/x; k = xy = 3(3) = 9, then y = 9/x.

see plot of 1) y = 10^x and 2) y = 9/x