Calculus: Solving differential equation e^y(1+dy/dx)=1 Also, to solve the equation explicitly: y(0)=ln(3)

Demarion Ortega

Demarion Ortega

Answered question

2022-11-05

Calculus: Solving differential equation e^y(1+(dy)/(dx))=1
I'm assuming this is will break down into a separable differential equation once some algebra has been applied but I can't figure out how to go about it.
It's the first time I encounter a differential equation containing e y
I started out distributing and then rewriting into e y + d y d x e y = 1, don't know if that's on the right track. I also tried rewriting with natural logarithm ln.
Also, to solve the equation explicitly: y ( 0 ) = ln ( 3 )

Answer & Explanation

barene55d

barene55d

Beginner2022-11-06Added 23 answers

e y + d y d x e y = 1
Let z = e y , then d z d x = e y d y d x
From ( 1 ), z + d z d x = 1
Since the above equation is a first order differential equation, so Integrating factor (I.F.) is e x . Now multiplying both side of the above equation by I.F. and the integrating we have
z e x = e x + c z = 1 + c e x e y = 1 + c e x
Given that y ( 0 ) = ln ( 3 ) 3 = 1 + c c = 2
Hence e y = 1 + 2 e x y = ln ( 1 + 2 e x )
gfresh86iop

gfresh86iop

Beginner2022-11-07Added 3 answers

We get
e y d y 1 e y = d x ln ( 1 e y ) = x + C y = ln ( 1 D e x ) .
Using y ( 0 ) = ln 3, finally the solution is y = ln ( 1 + 2 e x ) .

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