Q37 / 82 · NTA Abhyas (JEE Main) 2020 · Mathematics · Quadratic Equation

Let α and β are the roots of equation ax2+bx+c=0 a≠0. If 1, α+β, αβ are in arithmetic progression and α, 2, β are in harmonic progression, then the value of α2+β2-2α2β22α2+β2 is equal to

  • A
    0
  • B
    0.5
  • C
    1
  • Correct answer
    D
    1.5

Solution

1, α+β,αβ are in A.P. ⇒1,-ba,ca are in A.P.
⇒1+ca=-2ba⇒a+c+2b=0 … 1
1α,12,1β are in A.P. ⇒1α+1β=1⇒α+β=αβ
⇒-ba=ca⇒b+c=0 … 2
From 1 & 2 we get,
 a=-b=c
⇒α,β are roots of equation x2-x+1=0
Now, α2+β2-2α2β22α2+β2=12-(αβ)2(α+β)2-2αβ
=12-1212-21=12+1=1.5

Hence, the correct answer is option: 'D'.

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