If f(x)=1/(4x^2  + 2x + 1);x∈R, then find the maximum value of f(x).

If f(x) = 1/(4x^2 + 2x + 1), then find the maximum value of f(x) - CBSE Class 12 Sample Paper for 2024 Boards

part 2 - Question 23 (Choice 1) - CBSE Class 12 Sample Paper for 2024 Boards - Solutions of Sample Papers and Past Year Papers - for Class 12 Boards - Class 12
part 3 - Question 23 (Choice 1) - CBSE Class 12 Sample Paper for 2024 Boards - Solutions of Sample Papers and Past Year Papers - for Class 12 Boards - Class 12 part 4 - Question 23 (Choice 1) - CBSE Class 12 Sample Paper for 2024 Boards - Solutions of Sample Papers and Past Year Papers - for Class 12 Boards - Class 12 part 5 - Question 23 (Choice 1) - CBSE Class 12 Sample Paper for 2024 Boards - Solutions of Sample Papers and Past Year Papers - for Class 12 Boards - Class 12

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f(š‘„)=1/(4š‘„^2 + 2š‘„ + 1) Finding f’(š’™) f’(š‘„)= ((1)^′ " " (4š‘„^2 + 2š‘„ + 1)" āˆ’ " (怖4š‘„^2 + 2š‘„ + 1)怗^′ (1))/((怖4š‘„^2 + 2š‘„ + 1)怗^2 ) f’(š‘„)= (0 (4š‘„^2 + 2š‘„ + 1)" āˆ’ " (8š‘„ + 2)(1))/((怖4š‘„^2 + 2š‘„ + 1)怗^2 ) f’(š‘„)= ("āˆ’" (8š‘„ + 2) )/((怖4š‘„^2 + 2š‘„ + 1)怗^2 ) Putting f’(š’™)=šŸŽ ("āˆ’" (8š‘„ + 2) )/((怖4š‘„^2 + 2š‘„ + 1)怗^2 ) = 0 -(8x + 2) = 0 8x + 2 = 0 8x = -2 āˆ’(8x + 2) = 0 8x + 2 = 0 8x = āˆ’2 x = (āˆ’2)/8 x = (āˆ’šŸ)/šŸ’ Finding f’’(š’™) f’(š‘„)=("āˆ’" (8š‘„ + 2) )/((怖4š‘„^2 + 2š‘„ + 1)怗^2 ) " " Differentiating again w.r.t x f’’(x) =āˆ’((8š‘„ + 2)^′ (怖4š‘„^2 + 2š‘„ + 1)怗^2āˆ’((怖4š‘„^2+2š‘„+1)怗^2 )^′ (8š‘„ + 2))/(((怖4š‘„^2 + 2š‘„ + 1)怗^2 )^2 ) f’’(x) =āˆ’(8(怖4š‘„^2 + 2š‘„ + 1)怗^2 āˆ’ 2(4š‘„^2 + 2š‘„ + 1)(8š‘„ + 2)(8š‘„ + 2))/(4š‘„^2 + 2š‘„ + 1)^4 f’’(x) =āˆ’(8(怖4š‘„^2 + 2š‘„ + 1)怗^2 āˆ’ 2(4š‘„^2 + 2š‘„ + 1)(8š‘„ + 2)(8š‘„ + 2))/(4š‘„^2 + 2š‘„ + 1)^4 f’’(x) =āˆ’(8(怖4š‘„^2 + 2š‘„ + 1)怗^2 āˆ’ 2(4š‘„^2 + 2š‘„ + 1) (8š‘„ + 2)^2)/(4š‘„^2 + 2š‘„ + 1)^4 f’’ (āˆ’šŸ/šŸ’) = āˆ’(8(怖4(āˆ’1/4)^2+ 2(āˆ’1/4) + 1)怗^2 āˆ’ 2(4(āˆ’1/4)^2+ 2(āˆ’1/4)+ 1) (8(āˆ’1/4)+ 2)^2)/(4(āˆ’1/4)^2+ 2(āˆ’1/4)+ 1)^4 f’’ (āˆ’šŸ/šŸ’) = āˆ’(8(怖4(āˆ’1/4)^2+ 2(āˆ’1/4) + 1)怗^2 āˆ’ 2(4(āˆ’1/4)^2+ 2(āˆ’1/4)+ 1) (āˆ’2 + 2)^2)/(4(āˆ’1/4)^2+ 2(āˆ’1/4)+ 1)^4 f’’ (āˆ’šŸ/šŸ’) = āˆ’(8(3/4)^2āˆ’0)/(3/4)^4 = āˆ’8/(3/4)^2 f’’ (āˆ’šŸ/šŸ’) < 0 Since f’’ (āˆ’šŸ/šŸ’) < 0 , š‘„ = āˆ’šŸ/šŸ’ is point of local maxima Putting š‘„ = āˆ’šŸ/šŸ’ , we can calculate maximum value f(š‘„) =1/(4š‘„^2+2š‘„+1) f(āˆ’šŸ/šŸ’)=1/(4(āˆ’1/4)^2+ 2(āˆ’1/4)+ 1) =1/(4(1/16)+ 2(āˆ’1/4)+ 1) =1/(1/4 āˆ’ 2/4+ 1) = 4/(1 āˆ’2+ 4) = šŸ’/šŸ‘

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