lf p,q,r∈R and the quadratic equation px2+qx+r=0 has no real root, then
A
p(p+q+r)>0
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B
p+q+r=0
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C
q(p+q+r)>0
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D
p+q+r>0
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Solution
The correct option is Ap(p+q+r)>0 ∵px2+qx+rhasnorealrootsthentherootsareω,ω2.Whenω3=1and1+ω+ω2=0.∴ω+ω2=−qp⇒−1=−qp⇒p=q.....(1)Again,ω.ω2=rp⇒1=rp⇒r=p......(2)∴From(1)and(2)p=q=r......(3)Now,p>0∴p(p+q+r)=p(3p)[from(3)]=3p2>0(∵p>0)∴p(p+q+r)>0AnsOptionA.