simple

Lt x→0 (1+3x+2x2)^(1/x)

25 Answers

1
Philip Calvert ·

okie
lets leave this part to prophet then :) we enjoy reading his posts
(though we don't understand much) [1]

11
Subash ·

thanx a lot for the proof

341
Hari Shankar ·

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)

62
Lokesh Verma ·

it is now ;)

11
Subash ·

thanx prophet for another method

bhaiyya why isnt this pinked

341
Hari Shankar ·

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

11
Subash ·

bhaiya i see it that complete proof is not necessary

but ur proof doesnt solve this problem either

or does it

11
Subash ·

i understand ur steps

but how does it prove the initial statement

62
Lokesh Verma ·

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

11
Subash ·

btw pink is better than green solutions are beautiful

11
Subash ·

some one please reply

11
Subash ·

shud i just remember the formula for tis one

62
Lokesh Verma ·

haha..

I sometimes start to wonder if he is still preparing for JEE... :)

1
Philip Calvert ·

e3

62
Lokesh Verma ·

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!)

62
Lokesh Verma ·

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?

1
Philip Calvert ·

[7][7][7]
[7][7][7]
clueless how does this prove e^(Ltx→0f(x)-1)g(x)

62
Lokesh Verma ·

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 :)

11
Subash ·

guyz i know this is a silly question

but plz give me the proof for that

3
msp ·

i am also getting e3

mtd: take log and use l'hopital rule

11
Subash ·

how do u get the e^(Ltx→0f(x)-1)g(x) thing

13
MAK ·

oops... i'm late... [6]

13
MAK ·

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]

1
Philip Calvert ·

e(f(x)-1)g(x)
for ltx→0 f(x)g(x)
where f(x)→1 and g(x) → ∞ when x→0

11
Subash ·

can u pls show ur method

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