60. (x2+xy)dy=(x2+y2)dx

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1 Answer
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8 months ago

The given D.E. is

dydx=x2+y2x2+x+y=x2(1+y2x2)x2(1+yx)=F(x,y)Then,F(λx,λy)=λ2x2λ2x2[1+λ2y2λ2x21+λyλx]=λ0F(x,y)=λ2F(x,y)

Hence, F(x,y) is a homogenous fxn of degree 2.

To solve it, let

y=vx,sothat,dydx=v.dxdx+xdvdxv=yxdydx=v+xdvdx

The D.E. now becomes,

v+xdvdx=1+v21+vxdvdx=1+v21+vv=1+v2vv21+v=1v1+v(1+v1v)dv=dxx

Integrating both sides,

1+v1vdv=dxx1+v1vdv=logx+c2(1v)1vdv=logx+c21vdv1dv=logx+c2log|1v|1v=logx+clog(1v)2+v=logxc

Put v=yx,

log(1yx)2+y2=logx+clog(xyx)2+logx=yxc

log[(xyx)2*x]=yxcxyx=eyxc=c1eyxc,where,c1e

(xy)2=c1.xeyx is the required solution of the D.E.

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