Check sibling questions


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Ex 6.2, 5 Find the intervals in which the function f given by f (๐‘ฅ) = 2๐‘ฅ3 โ€“ 3๐‘ฅ2 โ€“ 36๐‘ฅ + 7 is (a) strictly increasing (b) strictly decreasingf(๐‘ฅ) = 2๐‘ฅ3 โ€“ 3๐‘ฅ2 โ€“ 36๐‘ฅ + 7 Calculating fโ€™(๐’™) fโ€™(๐‘ฅ) = 6๐‘ฅ2 โ€“ 6๐‘ฅ โ€“ 36 + 0 fโ€™(๐‘ฅ) = 6 (๐‘ฅ2 โ€“ ๐‘ฅ โ€“ 6 ) fโ€™(๐‘ฅ) = 6(๐‘ฅ^2 โ€“ 3๐‘ฅ + 2๐‘ฅ โ€“ 6) fโ€™(๐‘ฅ) = 6(๐‘ฅ(๐‘ฅ โˆ’ 3) + 2 (๐‘ฅ โˆ’ 3)) fโ€™(๐’™) = 6(๐’™ โ€“ 3) (๐’™ + 2) Putting fโ€™(x) = 0 6(๐‘ฅ+2)(๐‘ฅ โ€“3)=0 (๐‘ฅ+2)(๐‘ฅ โ€“3)=0 So, x = โˆ’2 and x = 3 Plotting points on number line Hence, f is strictly increasing in (โˆ’โˆž ,โˆ’๐Ÿ) & (๐Ÿ‘ ,โˆž) f is strictly decreasing in (โˆ’๐Ÿ, ๐Ÿ‘)

  1. Chapter 6 Class 12 Application of Derivatives
  2. Serial order wise

About the Author

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo