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Ask iit jee aieee pet cbse icse state board community Discussion Response Post to: Quadratic
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[Post New] 11 Mar 2007 16:19:22 IST
   Subject: Re:Quadratic
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CooldudeRama17 (115)

Olaaa!! Perrrfect answer. 21  [26 rates]
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If px2+qx+r=0 cannot have real roots then prove that r(p+q+r)>0
if it cannot have real roots
b2-4ac<0
q2-4pr<0
 
we take a function
f(x)=px2+qx+r
f(1)=p+q+r
now we should know that f(x) is a parabola and
f(1)>0 if  r>0
f(1)<0 if  r<0
 r.f(1)>0  because
positive*positive=positive
and negetive*negetive=positive
 
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  this reply:   5 points  (with 1  Olaaa!! Perrrfect answer.   in 1   votes   )     [?]
 
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