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![[Post New]](/templates/default/images/icon_minipost_new.gif) 24 Mar 2008 10:12:37 IST
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Q.f:R R given by f(x)=x3+ax2+bx+c is a bijection iff? 1.a2>or equal to 3b 2.a2<or equal to 3b 3.a2=3b 4.none
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it is 2.. a2<3b
the function is onto
to be one-one it should be monotonically increasing in its entire domain
use that condition
u will get 2
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24 Mar 2008 10:55:30 IST
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A bijective function is one that is both one-one and onto. A one-ono function is always in increasing or decreasing in its domain.
The minimum value of the first term is 0 and occurs when  . Hence for the function to be one-one  .
 Hence B. edit: corrected mistake.
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Guide to latex:
http://www.goiit.com/posts/list/community-shelf-a-guide-to-latex-48056.htm
JEE and OLYMPIA INFINATUM
http://iit-redefined.theforum.name/index.php
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24 Mar 2008 11:15:55 IST
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the question says "iff" which means if and only if .
option B says "less than or equal to" . so B is the only correct option
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24 Mar 2008 11:24:22 IST
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yeah didnt see that it said "less than or equal to"
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Guide to latex:
http://www.goiit.com/posts/list/community-shelf-a-guide-to-latex-48056.htm
JEE and OLYMPIA INFINATUM
http://iit-redefined.theforum.name/index.php
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