If α ,   β are the real roots of x 2 + p x + q = 0 and α 4 ,   β 4 are the…

If α, β are the real roots of x2+px+q=0 and α4, β4 are the roots of x2-rx+s=0, then the equation x2-4qx+2q2-r=0 has always
  1. two positive roots
  2. two negative roots
  3. one positive root and one negative root
  4. two real roots

Solution

It is given that, α, β are the roots of x2+px+q=0
α+β=-p and αβ=q
Since, α4, β4 are roots of x2-rx+s=0

Therefore, α4+β4=r and α4β4=s
Now, x2-4qx+2q2-r=0

D=(4q)2-42q2-r

=16q2-8q2+4r

=8q2+4r

Here, r=α4+β40 and 8q20.
Thus, D0

Therefore, the equation has two real roots.

Asked in: AP EAMCET 2019 (21 Apr Shift 2)

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