If α , β are the roots of the equation x 2 - 5 + 3 log 3 5 - 5 log 5 3 x + 3 3 log 3 5 1 3 - 5 log…

If α,β are the roots of the equation x2-5+3log35-5log53x+33log3513-5log5323-1=0 then the equation, whose roots are α+1β and β+1α,
  1. 3x2-20x-12=0
  2. 3x2-10x-4=0
  3. 3x2-10x+2=0
  4. 3x2-20x+16=0

Solution

Given α,β are the roots of the equation x2-5+3log35-5log53x+33log3513-5log5323-1=0

Now 3log35-5log53=3log35-3log35log53

=3log35-3log35=0

Also 3log3513-5log5323=5log5323-5log5323

=0

So, given equation becomes x2-5x-3=0 

i.e. α+β=5; αβ=-3

Now if the roots are $\alpha + \frac{1}{\beta}$ and $\beta + \frac{1}{\alpha}$ i.e., $\frac{\alpha \beta + 1}{\beta}$ and $\frac{\alpha \beta + 1}{\alpha}$ i.e., $-\frac{2}{\beta}$ and $-\frac{2}{\alpha}$ Then let $-\frac{2}{\alpha} = t so \alpha = -\frac{2}{t}$ As $\alpha^2 - 5\alpha - 3 = 0$ Then $(-\frac{2}{t})^2 - 5(-\frac{2}{t}) - 3 = 0$ Which simplifies to $\frac{4}{t^2} + \frac{10}{t} - 3 = 0$ And further simplifies to $3t^2 - 10t - 4 = 0$ i.e., $3x^2 - 10x - 4 = 0$ is the required equation.

Asked in: JEE Main 2022 (27 Jul Shift 2)

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