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![[Post New]](/templates/default/images/icon_minipost_new.gif) 15 Jun 2008 09:43:18 IST
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1)if a+b+c=0 then the equation 3ax^2 +2bx+c has in the interval(0,1)
a at least one root b at the most one root c no root d none of these
2)if 27a+9b+3c+d=0 then the equation 4ax^3+3bx^2+2cx+d=0 has at least one root lying b/w
a 0 and 1 b 1and3 c 0and 3 dnone of these
plz ans as soon as possible!!!!
rates for proper exp
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 15 Jun 2008 09:59:50 IST
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1) a i think... if f(0)>0 v get f(2/3)<0 n vice versa if f(1/3)>0 then f(1)<0 n vice versa
so between 0 and 2/3 therer is a root similarly there is a root between 1/3 and 1...these 2 roots may be same or diff...so there is atleast 1 root
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 15 Jun 2008 10:03:05 IST
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ur ans looks correct but then whats the use of equation a+b+c=0???
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 15 Jun 2008 10:06:02 IST
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only using that i get:
if f(0)>0 v get f(2/3)<0 n vice versa
if f(1/3)>0 then f(1)<0 n vice versa
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 15 Jun 2008 10:09:22 IST
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cud u plz be aliitle elaborate???
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 15 Jun 2008 10:10:24 IST
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2)
consider the eqn:
g(x)=ax^4 + bx^3 + cx^2 +dx +e
here g'(x)=eqn u mentioned in the question
g(0)=e
g(3) also =e
so g(0)=g(3)
hence from rolles theorem there exists values of x (0,3) such tht g'(x)=0
these values may be 1 or more
hence the answer is atleast 1 root in (0,3)
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 15 Jun 2008 10:12:54 IST
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1)consider g(x)=ax^3 + bx^2 + cx +d
g(0)=d
g(1)=a+b+c+d=d(as a+b+c=0)
g(0)=g(1)...from rolles theorem there exist atleast 1 value in (0,1) such tht g'(x)=0
note tht g'(x) = the eqn u have given
hence ans is ---atleast 1 root
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 15 Jun 2008 10:17:45 IST
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thks!!!
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