+1 vote
in General by kratos

For the following differential equation find the particular solution satisfying the given condition:

$("x" + 1) "dy"/"dx" - 1 = 2"e"^-"y" , "y" = 0$, when x = 1

1 Answer

+2 votes
by kratos
 
Best answer

$("x" + 1) "dy"/"dx" - 1 = 2"e"^-"y"$

$("x" + 1) "dy"/"dx" = 2/"e"^"y" + 1 = (2 + "e"^-"y")$

$"e"^"y"/(2 + "e"^-"y") "dy" = 1/("x" + 1)$dx

Integrating both sides, we get

$int "e"^"y"/(2 + "e"^-"y") "dy" = int 1/("x" + 1)$dx

log |2 + ey| = log |x + 1| + log c ......$[ "d"/"dy" (2 + "e"^"y") = "e"^"y" and int("f"'("y"))/("f"("y")) "dy" = log |"f"("y")| + "c"]$

log |2 + ey| = log |c (x + 1)|

2 + ey = c(x + 1)

This is the general solution.

Now, y = 0, when x = 1

2 + e0 = c (1 + 1)

3 = 2c

c = $3/2$

the particular solution is $2 + "e"^"y" = 3/2("x" + 1)$

2(2 + ey) = 3(x + 1)

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