Q.
If the two equations x3−cx+d=0 and x3−ax+b=0 have one common root and the second equation has equal roots, then 2(b+d)=
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Complex Numbers and Quadratic Equations
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Solution:
(x−2a)2=(4a2−b) ⇒a2=4b..........(i) x=2a.............(ii) α2−cα+d=0 α2−aα+b=0 α=(c−ad−b) and from (ii) is 2a 2a=c−ad−b=2d−2b=ac−a2 { from (i) a2=4b} 2(b+d)=ac