sign up I login
 advanced
refer a friend - earn nickels!!

Ask & Discuss Questions with Community & Experts

Moderation Team
 90 chars left    advanced
Ask iit jee aieee pet cbse icse state board experts Expert Question: please solve it
Forum Index -> Differential Calculus like the article? email it to a friend.  
Author Message
bosedebjit (0)

New kid on the Block

Olaaa!! Perrrfect answer. 0  [0 rates]

bosedebjit's Avatar

total posts: 4    
offline Offline
If f(x) is twice differentiable and f(a)=0,f(b)=2,f(c)= -1,f(d)=2,f(e)=0,where a<b<c<d<e then find the minimum number of zeroes of g(x)={f'(x)2 +{f''(x)f(x)} in [a,e]
    
kaymant (1264)

Forum Expert Blazing goIITian

Olaaa!! Perrrfect answer. 234  [281 rates]

kaymant's Avatar

total posts: 352    
offline Offline

Re:please solve it


 this reply: 0 points  (with Olaaa!! Perrrfect answer.   in 0 votes )   [?]
 
You have to be logged on to rate
  
ankurgupta91 (828)

Scorching goIITian

Olaaa!! Perrrfect answer. 140  [204 rates]

ankurgupta91's Avatar

total posts: 245    
offline Offline
let h(x) = f(x)f`(x)
and then g(x) = h`(x)

nw h(x) = 0
when f(x) = 0 or f`(x) =0
btw [a,e] f(x) = 0 is at two pts i.e x=a and x=e
and btw (b,c) and (c,d) f(x) changes sign
so btw these intervals f(x) =0 at two more pts
thus, f(x) =0 at exactly four pts btw[a,e]

nw f`(x) = 0 at three pts
see btw (a,c) there wl be a local maximum at which f`(x) =0
and btw (b,d) there wl be a local minimum at which f`(x) =0
and btw ( c,e) there wl be a local maximum at which f`(x) = 0

so h(x) = 0 at seven points
nw applying rolle theorem ,
h`(x) =0 for atleast six pts

thus, the minimum roots of g(x) is six

thats the answer .......
hope u gt it...

nobody is perfect......i m nobody..............
 this reply: 2 points  (with Olaaa!! Perrrfect answer.   in 1 votes )   [?]
 
You have to be logged on to rate
  
krishna.gopal (2397)

Forum Expert Blazing goIITian

Olaaa!! Perrrfect answer. 381  bad job dude!! I dont approve of this answer! 2  [631 rates]

krishna.gopal's Avatar

total posts: 2940    
offline Offline
Right answer ankur. Kaymant you just focused on points where f(x) = 0 but missed those where f'(x) = 0.

Krishna Gopal Singh
B.Tech Chemical Engg
IIT Delhi 2002
Currently doing PhD from IIT Delhi
 this reply: 0 points  (with Olaaa!! Perrrfect answer.   in 0 votes )   [?]
 
You have to be logged on to rate
  
kaymant (1264)

Forum Expert Blazing goIITian

Olaaa!! Perrrfect answer. 234  [281 rates]

kaymant's Avatar

total posts: 352    
offline Offline
well yes.. i actually missed out those points.. ankur is right.
 this reply: 0 points  (with Olaaa!! Perrrfect answer.   in 0 votes )   [?]
 
You have to be logged on to rate
  
 
Forum Index -> Differential Calculus
Go to:   

Top Offers for goIITians
Correspondence Courses
Brilliant Tutorials
Narayana Institute
Aakash Institute
Classroom/Crash Courses
Narayana - Kota , Delhi , Others
Brilliant Tutorials - Class , Crash
Aakash Institute - Medical , Engg
Online Test Series
Brilliant Tutorials
Narayana Institute
Aakash Institute
Mahesh Tutorials
AMITY      Sri Chaitanya