Ex 6.2, 6 Find the intervals in which the following functions are strictly increasing or decreasing: (b) 10 – 6𝑥 – 2𝑥2 Calculating f’(𝒙) f(𝑥) = 10 – 6𝑥 – 2𝑥2 f’(𝑥) = –6 – 4𝑥 f’(𝑥) = −2(3 + 2𝑥) Putting f’(𝒙) = 0 −2(3 + 2𝑥) = 0 3 + 2𝑥 = 0 2𝑥 = −3 𝒙 = (−𝟑)/𝟐 Plotting points on number line Hence, f is strictly decreasing for 𝒙 > (−𝟑)/𝟐 f is strictly increasing for x < (−𝟑)/𝟐

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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