Mathematics · Functions

JEE Main 2026 — 24 January, Evening Shift — Question 13

If the domain of the function f(x)=sin⁡−1(1x2−2x−2)f(x)=\sin ^{-1} \left(\frac{1}{x^{2}-2 x-2}\right), is (−∞,α]∪[β,γ]∪[δ,∞)(-\infty, \alpha] \cup[\beta, \gamma] \cup[\delta, \infty), then α+β+γ+δ\alpha+\beta+\gamma+\delta is equal to

  1. Option A:

    2

  2. Option B:

    4

    Correct
  3. Option C:

    3

  4. Option D:

    5

Answer: B

Step-by-step solution

−1≤2x2−2x−2≤1-1 \leq \frac{2}{x^{2}-2 x-2} \leq 1

1+x2−2x−2x2−2x−2≥0\frac{1+\mathrm{x}^{2}-2 \mathrm{x}-2}{\mathrm{x}^{2}-2 \mathrm{x}-2} \geq 0

⇒(x−1)2−2(x−1)2−3≥0 \Rightarrow \frac{(\mathrm{x}-1)^{2}-2}{(\mathrm{x}-1)^{2}-3} \geq 0

⇒(x−1−2)(x−1+2)(x−1−3)(x−1+3)≥0\Rightarrow \frac{(\mathrm{x}-1-\sqrt{2})(\mathrm{x}-1+\sqrt{2})}{(\mathrm{x}-1-\sqrt{3})(\mathrm{x}-1+\sqrt{3})} \geq 0

x∈(−∞,1−3)∪[1−2,1+2]∪(1+3,0)\begin{gathered} x \in(-\infty, 1-\sqrt{3}) \cup[1-\sqrt{2}, 1+\sqrt{2}] \cup(1+\sqrt{3}, 0) \end{gathered}

1−1x2−2x−2≥0⇒x2−2x−3x2−2x−2≥01-\frac{1}{\mathrm{x}^{2}-2 \mathrm{x}-2} \geq 0 \Rightarrow \frac{\mathrm{x}^{2}-2 \mathrm{x}-3}{\mathrm{x}^{2}-2 \mathrm{x}-2} \geq 0

⇒(x+1)(x−3)(x−1+3)(x−1−3)≥0\Rightarrow \frac{(\mathrm{x}+1)(\mathrm{x}-3)}{(\mathrm{x}-1+\sqrt{3})(\mathrm{x}-1-\sqrt{3})} \geq 0

x∈(−∞,−1]∪(1−3,3+1)∪[3,∞)∩(2)\begin{gathered} \mathrm{x} \in(-\infty,-1] \cup(1-\sqrt{3}, \sqrt{3}+1) \cup[3, \infty)\cap(2) \end{gathered}

⇒x∈(−∞,−1]∪[1−2,1+2]∪[3,∞)\Rightarrow \mathrm{x} \in(-\infty,-1] \cup[1-\sqrt{2}, 1+\sqrt{2}] \cup[3, \infty)

∴α+β+γ+δ=4\therefore \alpha+\beta+\gamma+\delta=4

Answer key and solution verified before publishing.

Practise Functions

Start with this question, then two more from the same chapter — with a tutor that explains every step. Free.

Exam
JEE Main 2026
Subject
Mathematics
Chapter
Functions
Topic
Domain & range of functions