Q43 / 118 · NTA Abhyas (JEE Main) 2020 · Mathematics · Sequences and Series

Let α, β and γ are the roots of the equation 2x3+9x2-27x-54=0. If α,β,γ are in geometric progression, then the value of α+β+γ=

  • A
    192
  • Correct answer
    B
    212
  • C
    13
  • D
    11

Solution

Let, α=βr and γ=βr
α⋅β⋅γ=βr⋅β⋅βr=542=27
⇒β3=27⇒β=3
α+β+γ=βr+β+βr=-92
⇒3r+3+3r=-92
⇒1r+1+r=-32
⇒2+2r+2r2=-3r
⇒2r2+5r+2=0
⇒2r+1r+2=0⇒r=-12,-2
α=βr=3-2=-32
β=3
γ=βr=3-2=-6
α+β+γ=32+3+6=212

Hence, the correct answer is option: 'B'.

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