JEE Main 2024 · MathsMultiple choiceSingle correctHardMulti-step

JEE Main 1 February 2024, Shift 1, Maths Q7

Question 7 of 90 in this shift, Maths question 7 of 30, Section A.

5f(x)+4f\left(\frac{1}{x}\right)=x^2-2,\ \forall\ x\neq0

and

y=9x^2f(x)

, then

y

is strictly increasing in :

(1) $\left(-\frac{1}{\sqrt{5}},0\right)\cup\left(0,\frac{1}{\sqrt{5}}\right)$
(2) $\left(-\infty,\frac{1}{\sqrt{5}}\right)\cup\left(0,\frac{1}{\sqrt{5}}\right)$
(3) $\left(-\frac{1}{\sqrt{5}},0\right)\cup\left(\frac{1}{\sqrt{5}},\infty\right)$ Official answer
(4) $\left(0,\frac{1}{\sqrt{5}}\right)\cup\left(\frac{1}{\sqrt{5}},\infty\right)$

Official answer

Option 3

NTA final key.

Chapter: Application of Derivatives
Topic: Monotonicity
Idea tested: Finding Intervals

Same idea in other shifts

Asked 7× in all

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.