log negative numbers

[jshaziza]

How would I calculate negative numbers using log or In. Whenever I try to do lets say log -10 it gives Ma error on my calculator; would I first put a negative sign before In or log and than put in the number with a positive sign?

 

[stapel]

You might want to study up first on logarithms. :idea:

. . . . .Google results for "logarithm"

. . . . .Google results for "log rules"

Once you know what logs are, you'll see why you can't take the log of a non-positive number. Also, you'll learn that the natural log is "ell-enn", not "capital-eye-enn". :wink:

Note: Since there was not specific exercise posted, there is little way to provide a specific answer or link. Sorry!

Eliz.

 

[jshaziza]

Thx. Stapel, I didn't know that since my book never mentioned it. But the specific exercise I am doing is graphing with log formulas and so I figured as with the other graphing I've done that I would plug in some numbers for x , as well as negative ones, and solve for y. But since I can't do negative numbers with log I'll just plug in positve ones although I don't know if that will mess up my graph or not. Thx. for the info.

 

[stapel]

I'll just plug in positve ones although I don't know if that will mess up my graph or not.

I'm sorry to hear that your book is assigning log questions without having covered logarithms. That must be very frustrating!

But which web lessons (from the links provided) did you study, that you are still not sure what a log is or whether you can plug negative numbers into a log? (I'd like to know which sites to avoid recommending!)

Thank you!

Eliz.

P.S. To be on the safe side, study here to learn what logs are, here to learn how to manipulate log terms, and here to learn how to graph them. These lessons should provide the information that was missing from your class, your book, and the web lessons you studied.

 

[jshaziza]

That last one was very helpful, thx. Stapel.