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JEE Main 202430 JanuaryMorning Shift
Exam
JEE Main
Year
2024
Date
30 January
Shift
Morning Shift
Subject
Mathematics
Chapter
Quadratic Equation

JEE Main 2024 · 30 January · Morning Shift · Mathematics · Quadratic Equation

Let (α, β ∈) be roots of equation (x^2-70 x+λ=0), where ((λ)/(2),...

Let (\alpha, \beta \in) be roots of equation (x^2-70 x+\lambda=0), where (\frac{\lambda}{2}, \frac{\lambda}{3} \notin). If (\lambda) assumes the minimum possible value, then (\frac{(\sqrt{\alpha-1}+\sqrt{\beta-1})(\lambda+35)}{\boldsymbol{|\alpha-\beta|}}) is equal to :

Correct answer

0

Step-by-step solution

Given,

x2−70x+λ=0{x}^{2} - 70x + \lambda = 0

Sum of the roots will be α+β=70\alpha + \beta = 70

Product of roots will be αβ=λ\alpha\beta = \lambda

⇒α(70−α)=λ⇒ \alpha ( 70 - \alpha ) = \lambda

⇒dλdα=70−2α⇒ \dfrac{d\lambda}{d\alpha} = 70 - 2\alpha

Now, λ\lambda is increasing for all α≤35\alpha \le 35

And 22 and 33 does not divide λ\lambda so taking  α=5\alpha = 5 we get, β=70−α=65\beta = 70 - \alpha = 65 

Asforα=1,β=69 and forα=4,β=66\text{As}\text{for}\alpha = 1, \beta = 69 \text{ and } \text{for}\alpha = 4, \beta = 66 which is not possible as they are multiple of 2 and 32 \text{ and } 3

Hence, α=5,β=65,λ=325\alpha = 5, \beta = 65, \lambda = 325

Now solving,

(α−1+β−1)(λ+35)∣α−β∣\dfrac{\left(\sqrt{\alpha - 1} + \sqrt{\beta - 1}\right)\left(\lambda + 35\right)}{| \alpha - \beta |}

=(5−1+65−1)(325+35)∣5−65∣= \dfrac{\left(\sqrt{5 - 1} + \sqrt{65 - 1}\right)\left(325 + 35\right)}{| 5 - 65 |}

=(2+8)⋅36060= \dfrac{\left(2 + 8\right) \cdot 360}{60}

=60= 60

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