The two roots of an equation x3−9x2+14x+24=0 are in the ratio 3:2, The roots will be
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a
6,4,−1
b
6,4,1
c
−6,4,1
d
−6,−4,1
answer is A.
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Detailed Solution
The given equation is x3−9x2+14x+24=0 Let the required roots are 3α,2α,β (∵ ratio of two roots are 3:2)∴ ∑α=3α+2α+β=−(−9)1=9 ⇒ 5α+β=9 …….(i) ∑αβ=3α.2α+2α.β+β.3α=14 ⇒ 5αβ+6α2=14 ……(ii)and αβγ=3α.2α.β=−24 ⇒ 6a2β=−24 or α2β=−4 .….(iii)From Eq. (i), β=9−5α , put the value of β in Eq. (ii)⇒ 5α(9−5α)+6α2=14 ⇒ 19α2−45α+14=0 ⇒ (α−2)(19α−7)=0 ∴ α=2 or 719 ∴ from Eq. (i), if α=2 , then β=9−5×2=−1 ∵α=2,β=−1 satisfy the equation (iii) so required roots are 6,4,−1 .