Question 8 - Formation of Differntial equation when general solution given - Chapter 9 Class 12 Differential Equations
Last updated at April 16, 2024 by Teachoo
Formation of Differntial equation when general solution given
Formation of Differntial equation when general solution given
Last updated at April 16, 2024 by Teachoo
Question 8 Form the differential equation of the family of ellipses having foci on 𝑦−𝑎𝑥𝑖𝑠 and center at origin. Equation of ellipse having center at origin (0, 0) & foci on y-axis is 𝑥^2/𝑏^2 +𝑦^2/𝑎^2 =1 ∴ Differentiating Both Sides w.r.t. 𝑥 𝑑/𝑑𝑥 [𝑥^2/𝑏^2 +𝑦^2/𝑎^2 ] = (𝑑(1))/𝑑𝑥 1/𝑏^2 [2𝑥]+1/𝑎^2 [2𝑦] 𝑑𝑦/𝑑𝑥=0 2𝑥/𝑏^2 +2𝑦/𝑎^2 . 𝑑𝑦/𝑑𝑥=0 Since it has two variables, we will differentiate twice 2𝑦/𝑎^2 𝑦′=(−2𝑥)/𝑏^2 𝑦/𝑎^2 𝑦′=(−𝑥)/𝑏^2 (𝑦/𝑥)𝑦′=(−𝑎^2)/〖 𝑏〗^2 (𝑦𝑦^′)/𝑥 = (−𝑎^2)/𝑏^2 Again differentiating both sides w.r.t. x ((𝑦𝑦^′ )^′ 𝑥 − (𝑑𝑥/𝑑𝑥)(𝑦𝑦^′ ))/𝑥^2 =0 (𝑦𝑦^′ )^′ 𝑥 − (1)(𝑦𝑦^′ )=𝟎×𝒙^𝟐 (𝑦𝑦^′ )^′ 𝑥 −𝑦𝑦^′=𝟎 (Using Quotient rule and Diff. of constant is 0) (𝒚𝒚^′ )^′ 𝑥 −𝑦𝑦^′=0 (𝒚^′ 𝒚^′+𝒚𝒚′′)𝑥 −𝑦𝑦^′=0 (〖𝑦^′〗^2+𝑦𝑦′′)𝑥 −𝑦𝑦^′=0 𝑥〖𝑦^′〗^2+𝑥𝑦𝑦^′′−𝑦𝑦^′=0 𝒙𝒚𝒚^′′+𝒙〖𝒚^′〗^𝟐−𝒚𝒚^′=𝟎 (Using Product rule)