Solution 1. To solve the DE Bernoulli equation,
dy/dx=y(xy6−1)
The standard form is
dxdy+P(x)y=f(x)yn
Where n is not equal to zero or one
dy/dx=xy7−y
dy/dx+y=xy7 −−−−−−−−−−−−−−>(1)
n=7
U=y1−n=y1−7=y−6
U=y−6
U−61=(y−6)−61 ⟹ y=U−61
dy/dx=−61U−67∗dxdu
61U−67dxdu+U−61=xU−67−−−−−−−−−−−>(2)
Multiply by (61U−67)
dxdu−6U1=−6x
y(x)=ϵ∫ρ(x)dx=ϵ∫−6dx=ϵ−6x
⟹y(x)=ϵ−6x
ϵ−6xdxdu−6ϵ−6xU=−6xϵ−6x
dxd[ϵ−6xU]=−6xϵ−6x
Integration:
ϵ−6xU=∫−6xϵ−6xdx
ϵ−6xU=xϵ−6x+61ϵ−6x+C
⟹U=x+61+ϵ−6xC
y−6=x+61+Cϵ6x−−−−−−−−−−−−−>Answer
2. To solve the DE Bernoulli equation.
xdxdy+y=y21
The standard form is
dxdy+P(x)y=f(x)yn
Where n is not equal to zero or one
dxdy+x1y=x1y−2−−−−−−−−−−−−>(1)
n=−2
U=y1−n=y1−(−2)=y3
U=y3
⟹y=U31
dxdy=31U−32dxdu
31U−32dxdu+x1U31=x1U−32−−−−−−−>(2)
Multiply by (3U−32)
dxdu+x3U1=x3
y(x)=ϵ∫ρ(x)dx=ϵ∫x3dx=ϵ3ln∣x∣=∣x3∣=x3
⟹y(x)=x3
x3dxdu+3x2U=3x2
dxd[x3U]=3x2
x3U=33x2+C
U=1+x3C
y3=1+xxC⟹y=(1+xxC)31−−−−−−−>Answer
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