Problem: Given two positive reals and , show that there is a continuous function that satisfies .
Solution: There are several special cases that are interesting to look at before we make a guess as to what type of function will be. First we consider the case . This immediately gives
.
It should not be too difficult to guess that is a solution to this, as well as any constant multiple of it. Now try and , resulting in
.
Looks a lot like Fibonacci, right? In fact, one possible function is just . That’s pretty convenient.
Notice how both of these illuminating examples are exponential functions, which leads us to guess that our function will be exponential as well. So, following this track, we set
so we simply need to solve
.
Unfortunately, the equation does not always have a solution (take and for example). But that’s ok and I’ll worry about it some other time. In any case we have found a function for whenever the equation has a solution in the reals.
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January 16th, 2008 at 8:38 pm
AHH JEFFREY!!!
I”M FAILING ADVANCED CALC!!!
we have our final tomorrow and i know basically nothing!!!
ok. i’m just surfing the web cuz i don’ t want to study
but i’ll go to my emo corner and study now …
February 6th, 2008 at 10:43 pm
Oh, Xuan.
It wasn’t that bad… for me >_>
I was reminded of BATH because Andreea just now found out about the question written about her and dating Qiaochu. I wanted to look over the test again.
I wonder if you ever look at this…
February 17th, 2008 at 11:31 am
My god.
I swear I already left a comment here. I must be going crazy.
I came back a while ago to look at BATH tests, and now I’m looking up Mu Alpha Theta stuff.
Advanced Calculus is, like… easy, coming from someone who actually reads the textbook >_>
February 17th, 2008 at 11:32 am
Oh.
Uhh… I didn’t see that before. Now I just look stupid.
Sorry about that.
March 20th, 2008 at 9:08 pm
Great blog, why don’t you continue it?