okie
lets leave this part to prophet then :) we enjoy reading his posts
(though we don't understand much) [1]
25 Answers
And about why Lt x→0 f(x)g(x) ≡ eLt x→0 [f(x)-1].g(x) when f(x) →1 and g(x) →∞ as x→0
First, we must have that the limit (f(x) - 1)g(x) as x→0 is finite
Let y = f(x)g(x). Hence log y = g(x) log f(x) = [log (1+f(x) - 1)/f(x) - 1] [g(x) (f(x)-1)]
Hence Lt x→0 log y = log Lt x→0 y (since log is a continuous function)
= Lt x→0 [log (1+f(x) - 1)/f(x) - 1] Lt x→0(f(x) - 1)g(x) (as both limits are finite)
= Lt f(x)-1→0 [log (1+f(x) - 1)/f(x) - 1] Lt x→0(f(x) - 1)g(x) = Lt x→0(f(x) - 1)g(x)
Hence Lt x→0 y = eLt x→0(f(x) - 1)g(x)
This one can be written as Ltx→0 (1+2x)1/x (1+x)1/x
Ltx→0 (1+x)1/x = e and Ltx→0 (1+2x)1/x = [Lt2x→0 (1+2x)1/2x]2 = e2
So the limit is e3
bhaiya i see it that complete proof is not necessary
but ur proof doesnt solve this problem either
or does it
there is no formula... to learn...
but if u are nto able to understand ti.. then learn it :)
there is no problem in learning this one..
but u should see th eproof from my last post
haha..
I sometimes start to wonder if he is still preparing for JEE... :)
it is provable i believe and comes from that..
if u want i can try to give the proof but trust me there is no need to go that deep..
among our "active" users i think only prophet understands that part well enuf... (not that it is bad to know.. but at this stage there are better things to know!)
well philip .. that is provable.. but it needs a bit of pure mathematics...
You know the most basic definiton the epsilon delta definiton of existance of limit?
[7][7][7]
[7][7][7]
clueless how does this prove e^(Ltx→0f(x)-1)g(x)
f(x)^g(x)=y
take log on both sides
g(x) log f(x) = log (y)
elog y=1
thus,
eg(x) log f(x) =1
hence proved :)
If Lt x→0 f(x)g(x) is of the form 1∞
then, the given limit is equivalent to eLt x→0 [f(x)-1].g(x)
Solve using above concept...
the answer will be e3
[1]
e(f(x)-1)g(x)
for ltx→0 f(x)g(x)
where f(x)→1 and g(x) → ∞ when x→0