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Solve the following differential equation: dx/dy + 8x = 5e^-3y

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Question

Solve the following differential equation:

`"dx"/"dy" + "8x" = 5"e"^(- 3"y")`

Sum
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Solution

`"dx"/"dy" + "8x" = 5"e"^(- 3"y")`

∴ `"dx"/"dy" + "2x" = 5/4"e"^(- 3"y")` .....(1)

This is the linear differential equation of the form

`"dx"/"dy" + "Px" = "Q"` where P = 2 and `"Q" = 5/4 "e"^(- 3"y")`

∴ I.F. = `"e"^(int "P dy") = "e"^(2 "dy") = "e"^("2y")`

∴ the solution of (1) is given by

`"x" * ("I.F.") = int "Q" * ("I.F.") "dy" + "c"_1`

∴ `"x" * "e"^(2"y") = int 5/4 "e"^(- 3"y") * "e"^"2y" "dy" + "c"_1`

∴ `"x" * "e"^(2"y") = 5/4 int "e"^-"y" "dy" + "c"_1`

∴ `"x"  "e"^(2"y") = 5/4 * ("e"^-"y")/-1 + "c"_1`

∴ 4xe2y = - 5e-y + 4c1

∴ 4xe2y + - 5e-y = c, where c = 4c1

This is the general solution.

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Chapter 6: Differential Equations - Miscellaneous exercise 2 [Page 217]

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Balbharati Mathematics and Statistics 2 (Arts and Science) [English] Standard 12 Maharashtra State Board
Chapter 6 Differential Equations
Miscellaneous exercise 2 | Q 5.7 | Page 217

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