Q.
If α and β be the roots of x2+px+q=0, then βα2+αβ2(ωα+ω2β)(ω2α+ωβ) is equal to (ω,ω2 are complex cube roots of unity)
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Complex Numbers and Quadratic Equations
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Solution:
Since, α and β are the roots of the equation x2+px+q=0, therefore α+β=−p and αβ=q
Now, (ωα+ω2β)(ω2α+ωβ) =α2+β2+(ω4+ω2)αβ(∵ω3=1) =α2+β2−αβ.(∵ω+ω2=1) =(α+β)2−3αβ =p2−3q
Also, βα2+αβ2=αβα3+β3 =αβ(α+β)3−3αβ(α+β) =qp(3q−p2) ∴ The given expression =qp(3q−p2)(p2−3q)=−pq