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← JEE Main 2026 · 6 Apr · Shift 2
MathematicsSingle correct+4 / -1Question 16 of 75

JEE Main 2026 · 6 Apr · Shift 2, Mathematics question 16

Let lim⁡x→2(tan⁡(x−2))(rx2+(p−2)x−2p)(x−2)2=5\displaystyle\lim_{x\to2}\frac{\left(\tan(x-2)\right)\left(rx^2+(p-2)x-2p\right)}{(x-2)^2}=5 for some r,p∈Rr,p\in\mathbf R. If the set of all possible values of q, 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 :

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Answer and worked solution

Official answer: C

The limit. tan⁡(x−2)x−2→1\dfrac{\tan(x-2)}{x-2}\to1, so the quadratic must vanish at 2: 4r−4=04r-4=0 gives r=1r=1. Then x2+(p−2)x−2p=(x−2)(x+p)x^2+(p-2)x-2p=(x-2)(x+p), and the limit is 2+p=52+p=5, so p=3p=3.

Roots of x2−3x+q=0x^2-3x+q=0 in (0, 2).

  • Real roots: q≤94q\le\tfrac94.
  • f(0)=q>0f(0)=q>0 and f(2)=q−2>0f(2)=q-2>0.
  • Vertex 32∈(0,2)\tfrac32\in(0,2).

So q∈(2,94]q\in\left(2,\tfrac94\right] and 4(α+β)=4⋅174=174(\alpha+\beta)=4\cdot\tfrac{17}4=17.

(C)