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Ask iit jee aieee pet cbse icse state board experts Expert Question: Some Good Questions
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c_001 (0)

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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 ,

    
iitkgp_bipin (6498)

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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


 


 


 


Bipin Kumar Dubey
Chemical Dept.
IIT Kharagpur

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allamraju (3437)

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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

MAKING A MISTAKE IS HUMAN BUT REPEATING IT IS IDIOTIC.
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bladeX (68)

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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


WALK NOT AS IF YOU RULE THE WORLD...
BUT AS IF YOU DON'T CARE WHO RULES IT....

MAN WOULD DO NOTHING IF HE WAITED UNTIL HE COULD DO IT SO WELL THAT NO OTHER BEING CAN FIND FAULT WITH IT..................NEWMAN
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me (120)

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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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c_001 (0)

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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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allamraju (3437)

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For 3rd question,as x tends to infinity,x+1,x+2 also tend to infinity.Let limf(x) as xinfinity be k,then limf(x+1) and limf(x+2) as xinfinity also are k and hence,

3k=k+5/k2k=5/k and hence,k=

MAKING A MISTAKE IS HUMAN BUT REPEATING IT IS IDIOTIC.
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