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JEE Main 202227 JulyEvening Shift
Exam
JEE Main
Year
2022
Date
27 July
Shift
Evening Shift
Subject
Mathematics
Chapter
Quadratic Equation

JEE Main 2022 · 27 July · Evening Shift · Mathematics · Quadratic Equation

If α, β are the roots of the equation x ^ 2 - (5 + 3 ^ _ 3 5 - 5 ^...

If α,β\alpha, \beta are the roots of the equation x2−(5+3log⁡35−5log⁡53)x+3(3(log⁡35)13−5(log⁡53)23−1)=0{x}^{2} - \left(5 + {3}^{\sqrt{\log_{3}5}} - {5}^{\sqrt{\log_{5}3}}\right)x + 3\left({3}^{\left(\log_{3}5\right)\dfrac{1}{3}} - {5}^{\left(\log_{5}3\right)\dfrac{2}{3}} - 1\right) = 0 then the equation, whose roots are α+1β\alpha + \dfrac{1}{\beta} and β+1α\beta + \dfrac{1}{\alpha},

Options

  1. A3x2−20x−12=03{x}^{2} - 20x - 12 = 0
  2. B3x2−10x−4=03{x}^{2} - 10x - 4 = 0
  3. C3x2−10x+2=03{x}^{2} - 10x + 2 = 0
  4. D3x2−20x+16=03{x}^{2} - 20x + 16 = 0

Correct answer

B. 3x2−10x−4=03{x}^{2} - 10x - 4 = 0

Step-by-step solution

Given α,β\alpha, \beta are the roots of the equation x2−(5+3log⁡35−5log⁡53)x+3(3(log⁡35)13−5(log⁡53)23−1)=0{x}^{2} - \left(5 + {3}^{\sqrt{\log_{3}5}} - {5}^{\sqrt{\log_{5}3}}\right)x + 3\left({3}^{\left(\log_{3}5\right)\dfrac{1}{3}} - {5}^{\left(\log_{5}3\right)\dfrac{2}{3}} - 1\right) = 0

Now 3log⁡35−5log⁡53=3log⁡35−(3log⁡35)log⁡53{3}^{\sqrt{\log_{3}5}} - {5}^{\sqrt{\log_{5}3}} = {3}^{\sqrt{\log_{3}5}} - {\left({3}^{\log_{3}5}\right)}^{\sqrt{\log_{5}3}}

=3log⁡35−3log⁡35=0= {3}^{\sqrt{\log_{3}5}} - {3}^{\sqrt{\log_{3}5}} = 0

Also 3(log⁡35)13−5(log⁡53)23=5(log⁡53)23−5(log⁡53)23{3}^{\left(\log_{3}5\right)\dfrac{1}{3}} - {5}^{\left(\log_{5}3\right)\dfrac{2}{3}} = {5}^{\left(\log_{5}3\right)\dfrac{2}{3}} - {5}^{\left(\log_{5}3\right)\dfrac{2}{3}}

=0= 0

So, given equation becomes x2−5x−3=0{x}^{2} - 5x - 3 = 0

i.e. α+β=5;αβ=−3\alpha + \beta = 5; \alpha\beta = - 3

Now if the roots are α+1β\alpha + \dfrac{1}{\beta} and β+1α\beta + \dfrac{1}{\alpha}

i.e., αβ+1β and αβ+1α\dfrac{\alpha\beta + 1}{\beta} \text{ and } \dfrac{\alpha\beta + 1}{\alpha}

i.e., −2β and −2α\dfrac{- 2}{\beta} \text{ and } \dfrac{- 2}{\alpha}

Then let −2α=t⇒α=−2t\dfrac{- 2}{\alpha} = t ⇒ \alpha = \dfrac{- 2}{t}

As α2−5α−3=0{\alpha}^{2} - 5\alpha - 3 = 0

⇒(−2t)2−5(−2t)−3=0⇒ {\left(\dfrac{- 2}{t}\right)}^{2} - 5\left(\dfrac{- 2}{t}\right) - 3 = 0

⇒4t2+10t−3=0⇒ \dfrac{4}{{t}^{2}} + \dfrac{10}{t} - 3 = 0

⇒3t2−10t−4=0⇒ 3{t}^{2} - 10t - 4 = 0

i.e., 3x2−10x−4=03{x}^{2} - 10x - 4 = 0 is the required equation.

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