Question
If the two equations x2−cx+d=0 and x2−ax+b=0 have one common root and the second has equal roots, then 2(b+d)=)
Answer: Option C
:
C
Let roots of x2−cx+d=0 beα,β then roots of x2−ax+b=0 beα,α
∴α +β = c,αβ = d,α +α =α, α2 = b
Hence 2(b+d)=2(α2+αβ)=2α(α+β)=ac
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:
C
Let roots of x2−cx+d=0 beα,β then roots of x2−ax+b=0 beα,α
∴α +β = c,αβ = d,α +α =α, α2 = b
Hence 2(b+d)=2(α2+αβ)=2α(α+β)=ac
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