Q.

If αandβ are the real roots of x2+px+q=0  and α4,β4 are the roots of x2rx+s=0,  then the equation x24qx+2q2r=0  has always

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a

two negative roots

b

two real roots

c

two positive roots

d

roots of the opposite sign

answer is A.

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Detailed Solution

The given equation is x2+px+q=0  …. ( 1 )

αandβ are the real roots of ( 1 )

Then sum of the roots : α+β=p,

Product of the roots :αβ=q

And

The given another equation is x2rx+s=0  …. ( 2 )

α4,β4 are the roots of ( 2 )

then sum of the roots :α4+β4=r,

product of the roots : α4β4=s

 r>0.  For the equation x24qx+2q2r=0,

Here a=1,b=4q,c=2q2r

Dicriminant D=16q24(2q2r)=8q2+4r>0            

      =8α2β2+4(α4+β4)=4(α2+β2)2

   equation has two real roots.

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