Solve for the general solution of the differential equation (x

Kelly Nelson

Kelly Nelson

Answered question

2021-12-31

Solve for the general solution of the differential equation (x+2y1)dx+(2x+4y3)dy=0 using Substitution Suggested by the Equation.

Answer & Explanation

ol3i4c5s4hr

ol3i4c5s4hr

Beginner2022-01-01Added 48 answers

Given differential equation (x+2y1)dx+(2x+4y3)dy=0
dydx=x+2y12x+4y3
dydx=x+2y12(x+2y)3 (1)
Put x+2y=v (2)
1+2dydx=dvdx
2dydx=dvdx1
dydx=12(dvdx1) (3)
Using (2) and (3) in (1), we get
12(dvdx1)=v12v3
dvdx1=2v12v3
dvdx=12v12v3
dvdx=2v32(v1)2v3=2v32v+22v3
dvdx=12v3
(2v3)dv=dx
Integrating both side we get
(2v3)dv=dx+c
2v223v=x+c
v23v+x=c
Juan Spiller

Juan Spiller

Beginner2022-01-02Added 38 answers

This is an exact equation. Integrate x+2y1 with respect to x to get x22+2xyx+ϕ(y)
Now differentiate with respect to y to get
2x+ϕ(y)=2x+4y3
so we need ϕ(y)=4y3 and one antiderivative is 2y23y. Thus the general solution is
x22+2xyx+2y23y=c
Without the fraction and consolidating the factor 2 in the arbitrary constant
x2+4xy2x+4y26y=c
Vasquez

Vasquez

Expert2022-01-09Added 669 answers

dydx=x+2y12x+4y3=u+122u=2u+14u,u=x+2y32,dudx=1+2dydx=122u+14u=24u=12u,2u du=1dx,u2=x+C,(x+2y32)2=x+C,
Someone else noticed the de is exact! The solution can simply be written down, and is
x22+2xy+2y2x3y=C

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