Question #209129

w=dependent variable

v=independendt variable


w(2v-w+1)dv+v(3v-4w+3)dw=0


1
Expert's answer
2021-07-19T10:45:47-0400

w(2vw+1)dv+v(3v4w+3)dw=0w(2v-w+1)dv+v(3v-4w+3)dw=0


(2vww2+w)dv+(3v24vw+3v)dw=0(2vw-w^2+w)dv+(3v^2-4vw+3v)dw=0


M(v,w)=(2vww2+w)    M(v,w)w=2v2w+1M(v,w)=(2vw-w^2+w) \implies {\partial M(v,w) \over \partial w}=2v-2w+1


N(v,w)=(3v24vw+3v)    N(v,w)v=6v4w+3N(v,w)=(3v^2-4vw+3v) \implies {\partial N(v,w) \over \partial v}=6v-4w+3


The differential equation is not exact since M(v,w)wN(v,w)v{\partial M(v,w) \over \partial w} \not = {\partial N(v,w) \over \partial v}

There is no integrating factor of the form p(v)p(v) or p(w)p(w)

Let's try another method

(2vww2+w)dv+(3v24vw+3v)dw=0(2vw-w^2+w)dv+(3v^2-4vw+3v)dw=0


(2vww2+w)dvdv+(3v24vw+3v)dwdv=0(2vw-w^2+w){dv\over dv}+(3v^2-4vw+3v){dw\over dv}=0


(2vww2+w)+(3v24vw+3v)dwdv=0(2vw-w^2+w)+(3v^2-4vw+3v){dw\over dv}=0


(2vww2+w)+(3v2dwdv4vwdwdv+3vdwdv)=0(2vw-w^2+w)+(3v^2{dw\over dv}-4vw{dw\over dv}+3v{dw\over dv})=0


2vww2+w+3v2dwdv4vwdwdv+3vdwdv=0..........(i)2vw-w^2+w+3v^2{dw\over dv}-4vw{dw\over dv}+3v{dw\over dv}=0 ..........(i)


Let u=vw    dudv=w+vdwdv    dwdv=dudvvuv2u=vw\implies {du\over dv}=w+v{dw\over dv} \implies {dw\over dv}={{du\over dv}\over v}-{u\over v^2} and Substituting this to equation (i)(i)


2vuv(uv)2+(uv)+3v2(dudvvuv2)4vuv(dudvvuv2)+3v(dudvvuv2)=02v{u\over v}-({u\over v})^2+({u\over v})+3v^2({{du\over dv}\over v}-{u\over v^2})-4v{u\over v}({{du\over dv}\over v}-{u\over v^2}) +3v({{du\over dv}\over v}-{u\over v^2})=0


The Variables cannot be separated further

Lets check if the differential equation is homogenous


(2vww2+w)+(3v24vw+3v)dwdv=0(2vw-w^2+w)+(3v^2-4vw+3v){dw\over dv}=0


(3v24vw+3v)dwdv=(2vww2+w)(3v^2-4vw+3v){dw\over dv}=-(2vw-w^2+w)



dwdv=(2vww2+w)(3v24vw+3v){dw\over dv}=-{(2vw-w^2+w)\over (3v^2-4vw+3v)}

The differential equation is not homogenous

\therefore The differential equation has no solution









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