Ok, as the title stated, I need some help with a little equation. Or part of one at least.

I'm trying to get x in a equation of the type: a^x=y

So what am I supposed to do to get x. I want to get it without trial and error and without a graphic solution.

So The Pit get your collective brain together and Help me, please.
a^x = y

x ln a = ln y

x = (ln y) / (ln a)
Quote by greennblue10
a^x = y

x ln a = ln y

x = (ln y) / (ln a)

42,
exactly 42
Out here you've gotta know where your towel is!
Ok, thanks. So what is (In). I'm trying to solve it with my calculator, so what function should I use?
The ln button...

Or if that's too confusing, the log button.
oh, so thats the one, me and my friend thought about using it, but it didn't come out right. Thanks again. This will really help me during the national tests Tuesday.

Thanks
It was : A office supply costs 15000 SEK to buy. Each year the value of said product drops by 30%. During which year will the value drop under 10% of the initial buy price?
by the 7th year it has fallen bellow 15000

so in between the 6th and year I get
Thats correct, thats what i get and thats what the key state.

Another question: Whats the difference between ln and log? Since I get the same answer using log and ln
log on your calculator is normally to the base 10

ln is always to the base e, and is the natural logarithm of e^x
Quote by Osten1770
Ok, thanks. So what is (In). I'm trying to solve it with my calculator, so what function should I use?

On a lot of calculators, the ln (that's an L, not an I, by the way) is under the key marked log, and you have to select it from the little menu. By 'A lot of calculators', I mean the TI-30 that seems to be the norm at most high schools.
<Han> I love Hitler
ok, I found it and actually saw that it was called ln and not in. And also I'm using the TI-82 Stats (which is a piece of crap). But it did solve the problem, and now I'll probably cut about 10-15 minutes solving problems of this type, not to mention how many more I'll save when my pqx program is done/perfected.