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JEE Main 20266 AprilEvening Shift
Exam
JEE Main
Year
2026
Date
6 April
Shift
Evening Shift
Subject
Mathematics
Chapter
Limits

JEE Main 2026 · 6 April · Evening Shift · Mathematics · Limits

Let _ x → 2 (( (x-2))(rx^2 + (p-2)x - 2p))/((x-2)^2) = 5 for some...

Let lim⁡x→2(tan⁡(x−2))(rx2+(p−2)x−2p)(x−2)2=5\lim\limits_{x \to 2} \dfrac{(\tan(x-2))(rx^2 + (p-2)x - 2p)}{(x-2)^2} = 5 for some r,p∈Rr, p \in \mathbb{R}. If the set of all possible values of qq, such that the roots of the equation rx2−px+q=0rx^2 - px + q = 0 lie in (0,2)(0, 2), be the interval (α,β](\alpha, \beta], then 4(α+β)4(\alpha + \beta) equals :

Options

  1. A1111
  2. B1313
  3. C1717
  4. D2121

Correct answer

C. 1717

Step-by-step solution

Given limit is lim⁡x→2tan⁡(x−2)x−2⋅rx2+(p−2)x−2px−2=5\lim\limits_{x \to 2} \dfrac{\tan(x-2)}{x-2} \cdot \dfrac{rx^2 + (p-2)x - 2p}{x-2} = 5

Since lim⁡x→2tan⁡(x−2)x−2=1\lim\limits_{x \to 2} \dfrac{\tan(x-2)}{x-2} = 1, we have:

lim⁡x→2rx2+(p−2)x−2px−2=5\lim\limits_{x \to 2} \dfrac{rx^2 + (p-2)x - 2p}{x-2} = 5

For the limit to exist, the numerator must be zero at x=2x = 2:

r(2)2+(p−2)(2)−2p=0r(2)^2 + (p-2)(2) - 2p = 0

4r+2p−4−2p=0⇒4r=4⇒r=14r + 2p - 4 - 2p = 0 \Rightarrow 4r = 4 \Rightarrow r = 1

Substituting r=1r = 1 into the limit expression:

lim⁡x→2x2+(p−2)x−2px−2=5\lim\limits_{x \to 2} \dfrac{x^2 + (p-2)x - 2p}{x-2} = 5

lim⁡x→2(x−2)(x+p)x−2=5\lim\limits_{x \to 2} \dfrac{(x-2)(x+p)}{x-2} = 5

lim⁡x→2(x+p)=5⇒2+p=5⇒p=3\lim\limits_{x \to 2} (x+p) = 5 \Rightarrow 2 + p = 5 \Rightarrow p = 3

The quadratic equation is rx2−px+q=0rx^2 - px + q = 0, which becomes x2−3x+q=0x^2 - 3x + q = 0.

For both roots of f(x)=x2−3x+q=0f(x) = x^2 - 3x + q = 0 to lie in the interval (0,2)(0, 2), the following conditions must hold:

1) Discriminant D≥0⇒(−3)2−4(1)(q)≥0⇒9−4q≥0⇒q≤94D \ge 0 \Rightarrow (-3)^2 - 4(1)(q) \ge 0 \Rightarrow 9 - 4q \ge 0 \Rightarrow q \le \dfrac{9}{4}

2) f(0)>0⇒q>0f(0) > 0 \Rightarrow q > 0

3) f(2)>0⇒22−3(2)+q>0⇒q−2>0⇒q>2f(2) > 0 \Rightarrow 2^2 - 3(2) + q > 0 \Rightarrow q - 2 > 0 \Rightarrow q > 2

4) The xx-coordinate of the vertex must lie in (0,2)⇒0<−(−3)2(1)<2⇒0<1.5<2(0, 2) \Rightarrow 0 < \dfrac{-(-3)}{2(1)} < 2 \Rightarrow 0 < 1.5 < 2, which is true.

Taking the intersection of all conditions, we get q∈(2,94]q \in (2, \dfrac{9}{4}].

Comparing this with (α,β](\alpha, \beta], we have α=2\alpha = 2 and β=94\beta = \dfrac{9}{4}.

Therefore, 4(α+β)=4(2+94)=8+9=174(\alpha + \beta) = 4(2 + \dfrac{9}{4}) = 8 + 9 = 17.

Answer: 1717
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