# Ex 9.3, 4 - Chapter 9 Class 12 Differential Equations

Last updated at Dec. 10, 2019 by Teachoo

Last updated at Dec. 10, 2019 by Teachoo

Transcript

Ex 9.3, 4 Form a differential equation representing the given family of curves by eliminating arbitrary constants ๐ and ๐. ๐ฆ=๐^2๐ฅ (๐+๐๐ฅ) The Number Of Times We Differentiate Is Equal To Number Of Constants ๐ฆ=๐^2๐ฅ (๐+๐๐ฅ) โด Differentiating Both Sides w.r.t. ๐ฅ ๐ฆ^โฒ=๐/๐๐ฅ [๐^2๐ฅ [๐+๐๐ฅ]] ๐ฆ^โฒ=๐[๐^2๐ฅ ]/๐๐ฅ.[๐+๐๐ฅ]+๐^(2๐ฅ ) ๐[๐ + ๐๐ฅ]/๐๐ฅ ๐ฆ^โฒ=ใ2๐ใ^2๐ฅ [๐+๐๐ฅ]+๐^2๐ฅ.๐ ๐ฆ^โฒ=๐^2๐ฅ [2๐+2๐๐ฅ+๐] Again differentiating w.r.t.x ๐ฆ^โฒ=๐/๐๐ฅ (๐^2๐ฅ [2๐+2๐๐ฅ+๐]) yโ = (๐ (๐^2๐ฅ))/๐๐ฅ [2๐+2๐๐ฅ+๐]+๐^2๐ฅ (๐ [2๐+2๐๐ฅ+๐])/๐๐ฅ yโ = 2๐^2๐ฅ [2๐+2๐๐ฅ+๐]+๐^2๐ฅร2๐ Putting yโ=๐^2๐ฅ [2๐+2๐๐ฅ+๐] yโ = 2yโ + ๐^2๐ฅร2๐ yโ = 2yโ + 2๐^2๐ฅ ๐ yโ โ 2yโ = 2๐^2๐ฅ ๐ Also, yโ โ 2y = ๐^2๐ฅ [2๐+2๐๐ฅ +๐]โ2๐^2๐ฅ (๐+๐๐ฅ) yโ โ 2y = 2a๐^2๐ฅ+2๐๐ฅ ๐^2๐ฅ+๐^2๐ฅ ๐โ2๐ใ ๐ใ^2๐ฅโ2๐๐ฅ ๐^2๐ฅ yโ โ 2y = (2๐ใ ๐ใ^2๐ฅโ2๐ใ ๐ใ^2๐ฅ )+(2๐๐ฅ ๐^2๐ฅโ2๐๐ฅ ๐^2๐ฅ )+๐^2๐ฅ ๐ yโ โ 2y = 0 + 0 + ๐^2๐ฅ ๐ yโ โ 2y = ๐^2๐ฅ ๐ Now ((1))/((2)) , (๐ฆ" โ 2๐ฆ)/(๐ฆ^(โฒ ) โ 2๐ฆ)=(2๐^2๐ฅ ๐)/(๐^2๐ฅ ๐) (๐ฆ^โฒโฒ โ 2๐ฆ^โฒ)/(๐ฆ^โฒโ2๐ฆ)= 2 yโ โ 2yโ = 2(yโ โ 2y) yโ โ 2yโ = 2yโ โ 4y yโ โ 2yโ โ 2yโ + 4y = 0 yโ โ 4yโ + 4y = 0 (As ๐ฆ=๐^2๐ฅ (๐+๐๐ฅ) ) Again differentiating w.r.t.x yโ =๐/๐๐ฅ (๐^2๐ฅ [2๐+2๐๐ฅ+๐]) yโ = (๐ (๐^2๐ฅ))/๐๐ฅ [2๐+2๐๐ฅ+๐]+๐^2๐ฅ (๐ [2๐+2๐๐ฅ+๐])/๐๐ฅ yโ = 2๐^2๐ฅ [2๐+2๐๐ฅ+๐]+๐^2๐ฅร2๐ Putting yโ=๐^2๐ฅ [2๐+2๐๐ฅ+๐] yโ = 2yโ + ๐^2๐ฅร2๐ yโ = 2yโ + 2๐^2๐ฅ ๐ yโ โ 2yโ = 2๐^2๐ฅ ๐ โฆ(1) Differentiating again w.r.t x ๐ฆ^โฒโฒโ2๐ฆ^โฒ=๐(๐^2๐ฅ.๐)/๐๐ฅ ๐ฆ^โฒโฒโ2๐ฆ^โฒ=2๐^2๐ฅ ๐ Dividing (1) and (2) i.e. ((2))/((1)) , (๐ฆ" โ 2๐ฆ)/(๐ฆ^(โฒ ) โ 2๐ฆ)=(2๐^2๐ฅ ๐)/(๐^2๐ฅ ๐) (๐ฆ^โฒโฒ โ 2๐ฆ^โฒ)/(๐ฆ^โฒโ2๐ฆ)= 2 yโ โ 2yโ = 2(yโ โ 2y) โฆ(2) yโ โ 2yโ = 2yโ โ 4y yโ โ 2yโ โ 2yโ + 4y = 0 yโ โ 4yโ + 4y = 0 is the required equation

Ex 9.3

Ex 9.3, 1
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Ex 9.3, 2 Deleted for CBSE Board 2021 Exams only

Ex 9.3, 3 Important Deleted for CBSE Board 2021 Exams only

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Chapter 9 Class 12 Differential Equations

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.