If f(x)=1/(4x^2 + 2x + 1);x∈R, then find the maximum value of f(x).
CBSE Class 12 Sample Paper for 2024 Boards
CBSE Class 12 Sample Paper for 2024 Boards
Last updated at August 8, 2026 by Teachoo
Transcript
f(š„)=1/(4š„^2 + 2š„ + 1) Finding fā(š) fā(š„)= ((1)^ā² " " (4š„^2 + 2š„ + 1)" ā " (ć4š„^2 + 2š„ + 1)ć^ā² (1))/((ć4š„^2 + 2š„ + 1)ć^2 ) fā(š„)= (0 (4š„^2 + 2š„ + 1)" ā " (8š„ + 2)(1))/((ć4š„^2 + 2š„ + 1)ć^2 ) fā(š„)= ("ā" (8š„ + 2) )/((ć4š„^2 + 2š„ + 1)ć^2 ) Putting fā(š)=š ("ā" (8š„ + 2) )/((ć4š„^2 + 2š„ + 1)ć^2 ) = 0 -(8x + 2) = 0 8x + 2 = 0 8x = -2 ā(8x + 2) = 0 8x + 2 = 0 8x = ā2 x = (ā2)/8 x = (āš)/š Finding fāā(š) fā(š„)=("ā" (8š„ + 2) )/((ć4š„^2 + 2š„ + 1)ć^2 ) " " Differentiating again w.r.t x fāā(x) =ā((8š„ + 2)^ā² (ć4š„^2 + 2š„ + 1)ć^2ā((ć4š„^2+2š„+1)ć^2 )^ā² (8š„ + 2))/(((ć4š„^2 + 2š„ + 1)ć^2 )^2 ) fāā(x) =ā(8(ć4š„^2 + 2š„ + 1)ć^2 ā 2(4š„^2 + 2š„ + 1)(8š„ + 2)(8š„ + 2))/(4š„^2 + 2š„ + 1)^4 fāā(x) =ā(8(ć4š„^2 + 2š„ + 1)ć^2 ā 2(4š„^2 + 2š„ + 1)(8š„ + 2)(8š„ + 2))/(4š„^2 + 2š„ + 1)^4 fāā(x) =ā(8(ć4š„^2 + 2š„ + 1)ć^2 ā 2(4š„^2 + 2š„ + 1) (8š„ + 2)^2)/(4š„^2 + 2š„ + 1)^4 fāā (āš/š) = ā(8(ć4(ā1/4)^2+ 2(ā1/4) + 1)ć^2 ā 2(4(ā1/4)^2+ 2(ā1/4)+ 1) (8(ā1/4)+ 2)^2)/(4(ā1/4)^2+ 2(ā1/4)+ 1)^4 fāā (āš/š) = ā(8(ć4(ā1/4)^2+ 2(ā1/4) + 1)ć^2 ā 2(4(ā1/4)^2+ 2(ā1/4)+ 1) (ā2 + 2)^2)/(4(ā1/4)^2+ 2(ā1/4)+ 1)^4 fāā (āš/š) = ā(8(3/4)^2ā0)/(3/4)^4 = ā8/(3/4)^2 fāā (āš/š) < 0 Since fāā (āš/š) < 0 , š„ = āš/š is point of local maxima Putting š„ = āš/š , we can calculate maximum value f(š„) =1/(4š„^2+2š„+1) f(āš/š)=1/(4(ā1/4)^2+ 2(ā1/4)+ 1) =1/(4(1/16)+ 2(ā1/4)+ 1) =1/(1/4 ā 2/4+ 1) = 4/(1 ā2+ 4) = š/š