(2y^{2}- 2xy + 3x)dx + (y + 4xy - x^{2})dy

namenerk

namenerk

Answered question

2021-12-30

(2y22xy+3x)dx+(y+4xyx2)dy=0

Answer & Explanation

twineg4

twineg4

Beginner2021-12-31Added 33 answers

(exsiny+2y)dx+(2xexsiny)dy=0
py=excosy+2
Qx=2exsiny
pyQx
The differential equation is not exact.
Linda Birchfield

Linda Birchfield

Beginner2022-01-01Added 39 answers

This is an exact differential equation, because,
My=4x and Nx=4y
DfDy=4xy
f(x,y)=2xy2+G(x)
Dxf(x,y)=(xy)2+G(x)
Now,
(Xy)2+G(x)=2y2+3x
Solving for G(x), we have
G(x)=Integral of [2y2+3x](xy)2 which is:
3x22+2xy2x4y22+k. …A
General solution becomes,
A+2xy2
karton

karton

Expert2022-01-09Added 613 answers

Solve for (dy(x))/(dx):
(dy(x))/(dx)=(x+4y(x)+9)/(4x+y(x)2)
Let x=t+1 and y=v2. This gives dx=dt and dy=dv:
(dv(t))/(dt)=(t+4(v(t)2)+8)/(4(t+1)+v(t)4)
Collect in terms of t and v(t):
(dv(t))/(dt)=(t+4v(t))/(4t+v(t))
Let v(t) = t u(t), which gives (dv(t))/(dt)=t(du(t))/(dt)+u(t):
t(du(t))/(dt)+u(t)=(t+4tu(t))/(4t+tu(t))
Simplify:
t(du(t))/(dt)+u(t)=(4u(t)1)/(u(t)+4)
Solve for (du(t))/(dt):
(du(t))/(dt)=(u(t)21)/(t(u(t)+4))
Divide both sides by (u(t)21)/(u(t)+4):
((du(t))/(dt)(u(t)+4))/(u(t)21)=1/t
Integrate both sides with respect to t:
integral ((du(t))/(dt)(u(t)+4))/(u(t)21)dt=integral1/tdt
Evaluate the integrals:
4tan1(u(t))1/2log(u(t)2+1)=log(t)+c1, where c1 is an arbitrary constant.
Substitute back for v(t) = t u(t):
4tan1(v(t)/t)1/2log(v(t)2/t2+1)=log(t)+c1
Substitute back for t=x1 and v=y+2:
Answer: 4tan1((y(x)+2)/(x1))1/2log((y(x)+2)2/(x1)2+1)=log(x1)+c1

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