JEE Main 2021 · MathsNumerical answerNumerical valueEasyMulti-step

JEE Main 31 August 2021, Shift 1, Maths Q83

Question 83 of 90 in this shift, Maths question 23 of 30, Section B.

If ‘R’ is the least value of ‘a’ such that the function

f(x)=x^2+\mathrm{a}x+1

is increasing on

[1, 2]

and ‘S’ is the greatest value of ‘a’ such that the function

f(x)=x^2+\mathrm{a}x+1

is decreasing on

[1, 2]

, then the value of

|\mathrm{R}-\mathrm{S}|

is __________.

Official answer

NTA final key.

Chapter: Application of Derivatives
Topic: Monotonicity
Idea tested: Parameter Range for Localized Monotonicity

Same topic in other shifts

All Monotonicity questions

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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.