If 1 α , 1 β are the roots of the equation a x 2 + b x + 1 = 0 ,   a ≠ 0 ,   a , b…

If 1α,1β  are the roots of the equation ax2+bx+1=0, a0, a,bR, then the equation xx+b3+a3-3abx=0 has roots:
  1. αβ and αβ
  2. α-32 and β-32
  3. αβ12 and α12β
  4. α32 and β32

Solution

ax2+bx+1=0 has roots 1α,1β

⇒   1α+1β=-ba      ...1

1αβ=1a    ...2

xx+b3+a3-3abx=0

 x2+b3-3abx+a3=0

Multiply and divide with a3, we get

   x2+a3b3a3-31abax+a3=0
From equations 1 & 2,
⇒   x2+αβ3/2-α1/2+β1/23αβ3-31αβα+βαβx+αβ3/2=0

⇒  x2-α3/2+β3/2x+α3/2β3/2=0

Roots are α32 and β32.

Asked in: JEE Main 2014 (09 Apr Online)

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