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![[Post New]](/templates/default/images/icon_minipost_new.gif) 22 May 2008 11:14:21 IST
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Ques. {(x/x+1)a + sin(1/x)}x
Solution given: e1-a
My solution : e
Ques . {x} denotes the fractional part of x. then ({x}/tan{x})
solution given : not in the option (none of these )
my solution :1
Ques. if f(x)=1/3{f(x+1)+[5/f(x+2)]} and f(x)>0 for all x belongs to R , then f(x)
Solution given : (5/2)1/2
Specially do the third Question ,
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 22 May 2008 11:38:30 IST
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For the 1st question :
put h = 1/x
{(1+h)-a + sinh}1/h
= (1-ah+h)1/h (after expanding both of the terms and neglecting higher powers)
= {1 + h(1-a)}1/h
it is in the form of 1infinity which is evaluated as f(x)g(x) = e{f(x) - 1}.g(x)
so above limit becomes eh(1-a)/h = e1-a
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Bipin Kumar Dubey
Chemical Dept.
IIT Kharagpur
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 22 May 2008 11:45:05 IST
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1)It is of the form 1infinity.So,the limit becomes
elim(x)[(x/x+1)^a+sin(1/x)-1] .But xsin(1/x) tends to 1 as x tends to infinity and hence it becomes e1+lim[ -x / ].
Now,In the numerator xa+1 cancels and coeff. of xa is -a.Hence the limit of this becomes -a and hence the ans is e1-a
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MAKING A MISTAKE IS HUMAN BUT REPEATING IT IS IDIOTIC. |
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 22 May 2008 13:53:01 IST
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ANSWER TO QS. 2
AS SO SMETIMES X IS AN INTEGER AND SOMETIME A FRACTIONAL NUMBER SO {X}
IS AN OSCILLATING FUNCTION BETWEEN [0,1) HENCE WE CAN NEVER PREDICT WHAT IT IS
NOW YOUR QUESTION {X } / TAN {X} FOR SOMEVALUE {X} IS 0 THEN ANSWER IS O
WHILE FOR SOME VALUE IT IS SAY 0.3 THEN IT IS O.3 / TAN 0.3 HENCE THE FUNCTION IF PLOTTED
IS PERIODIC WITH PERIOD 1 AND WOULD BE MOVING UP AND DOWN WITH UNDEFINED AND INTEGERS
SO LIMIT DOESN'T EXIST ............WE CAN'T PREDICT WHAT THE LIMIT IS
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 22 May 2008 14:22:00 IST
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3rd first of we should realise infinity = infinty + 1 =infinity + 2 as infinity is such a large number that add. 1 or 2 dont make any difference. denote f(infinity) = y we so get -------- y = 1/3{y + 5/y) or 3y = y + 5/y or 2y=5/y we get----- y = (5/2)^1/2
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 22 May 2008 18:16:57 IST
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In accordance to the second Ques.
Friend , I am not satisfied with your answer . What you are saying that the given function is an oscillating one but i reall disagree that when {x}=0 then the given function would be zero . Actually it is assuming 0/0 indeterminate form.
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 22 May 2008 18:25:32 IST
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For 3rd question,as x tends to infinity,x+1,x+2 also tend to infinity.Let limf(x) as x infinity be k,then limf(x+1) and limf(x+2) as x infinity also are k and hence,
3k=k+5/k 2k=5/k and hence,k= 
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