Mathematics · Functions

JEE Main 2025 — 29 January, Evening Shift — Question 45

If the domain of the function log⁡5(18x−x2−77)\log _{5}\left(18 \mathrm{x}-\mathrm{x}^{2}-77\right) is (α,β)(\alpha, \beta) and the domain of the function

log⁡(x−1)(2x2+3x−2x2−3x−4)\log _{(x-1)}\left(\frac{2 x^{2}+3 \mathrm{x}-2}{\mathrm{x}^{2}-3 \mathrm{x}-4}\right) is (γ,δ)(\gamma, \delta), then α2+β2+γ2\alpha^{2}+\beta^{2}+\gamma^{2} is equal to

  1. Option A:

    195

  2. Option B:

    174

  3. Option C:

    186

    Correct
  4. Option D:

    179

Answer: C

Step-by-step solution

f1(x)=log⁡5(18x−x2−77)\mathrm{f}_{1}(\mathrm{x})=\log _{5}\left(18 \mathrm{x}-\mathrm{x}^{2}-77\right)

∴18x−x2−77>0\therefore 18 \mathrm{x}-\mathrm{x}^{2}-77>0

x2−18x+77<0x^{2}-18 x+77<0

x∈(7,11),α=7,β=11x \in(7,11), \alpha=7, \beta=11

f2(x)=log⁡(x−1)(2x2+3x−2x2−3x−4)f_{2}(x)=\log _{(x-1)}\left(\frac{2 x^{2}+3 x-2}{x^{2}-3 x-4}\right)

∴x−1>0,x−1≠1,2x2+3x−2x2−3x−4>0\therefore \quad \mathrm{x}-1>0, \mathrm{x}-1 \neq 1, \frac{2 \mathrm{x}^{2}+3 \mathrm{x}-2}{\mathrm{x}^{2}-3 \mathrm{x}-4}>0

x>1,x≠2,(2x−1)(x+2)(x−4)(x+1)>0x>1, x \neq 2, \frac{(2 x-1)(x+2)}{(x-4)(x+1)}>0

x>1,x≠2x>1, x \neq 2,

∴x∈(4,∞)\therefore \mathrm{x} \in(4, \infty)

∴γ=4\therefore \gamma=4

∴α2+β2+γ2=49+121+16\therefore \alpha^{2}+\beta^{2}+\gamma^{2}=49+121+16

=186=186

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Subject
Mathematics
Chapter
Functions
Topic
Domain & range of functions
If the domain of the function log 5 (18 x - x 2 -77 ) is (α, β) and… | JEE Main 2025 PYQ with Solution · DhiX AI