# Ex 6.2,14

Last updated at Dec. 8, 2016 by Teachoo

Last updated at Dec. 8, 2016 by Teachoo

Transcript

Ex 6.2,14 Find the least value of a such that the function f given by π (π₯) = π₯2 + ππ₯ + 1 is strictly increasing on (1, 2). We have fο·π₯ο·― = π₯2 + aπ₯ + 1 Given f is strictly increasing on ο·1 ,2ο·― β fβο·π₯ο·― > 0 on ο·1 ,2ο·― fβο·π₯ο·― = π₯2 + aπ₯ + 1 fβο·π₯ο·― = 2π₯ + a. Thus, 2π₯ + a > 0 on ο·1 ,2ο·― β΄ When a > β2 , fο·π₯ο·― = π₯2 + aπ₯ + 1 is strictly increasing on ο·π , πο·― Hence, least value of a is β2

Chapter 6 Class 12 Application of Derivatives

Serial order wise

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CA Maninder Singh is a Chartered Accountant for the past 8 years. He provides courses for Practical Accounts, Taxation and Efiling at teachoo.com .