If α≠β, but α2=5α−3,β2=5β−3, then the equation whose roots are αβ and βα is
A
3x2+12x+3=0
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B
3x2−19x+3=0
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C
None of these
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D
x2−5x−3=0
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Solution
The correct option is B3x2−19x+3=0 First we will find the sum and product of roots of required eqution.
Here,S=αβ+βα=α2+β2αβ=5α−3+5β−3αβ[∵α2=5α−3β2=5β−3] S=5(α+β)−6αβandP=αβ⋅βα=1⇒P=1.α,β are roots of x2−5x+3=0.
Therefore α+β=5,αβ=3S=5(5)−63=193
As we know a quadratic equation with given roots is given by x2−(Sum of roots)x+Product of roots=0 ⇒x2−193x+1=0⇒3x2−19x+3=0