The given differential equation is ,
yzdx+(x2y−zx)dy+(x2z−xy)dz=0
We known that ,the necessary and sufficient condition of integrability of the given differential equation Pdx+Qdy+Rdz=0 is
P(∂z∂Q−∂y∂R)+Q(∂x∂R−∂z∂P)+R(∂y∂P−∂x∂Q)=0...........(1)
Now ,according to question,
P=yz,Q=(x2y−zx) and R=(x2z−xy)
Now ,
∂y∂P=z and ∂z∂P=y.∂x∂Q=(2xy−z) and ∂z∂Q=−x∂x∂R=(2xz−y) and ∂y∂R=−x
putting above all value in equation (1) ,we get ,
yz(−x+x)+(x2y−zx){(2xz−y)−(y)}+(x2z−xy){(z)−(2xy−z)}
=0+2(x3yz−x2y2−x2z2+xyz+x2z2−x3yz−xyz+x2y2)=0
Hence ,given differential equation is integrable.
To solve the given differential equation , we take
x=constant. ⟹ dx=0 .
∴ (x2y−zx)dy+(x2z−xy)dz=0
⟹ x2(ydy+zdz)−x(zdy+ydz)=0
⟹ x2(ydy+zdz)−xd(yz)=0
On integrating ,we get
2x2y2+2x2z2−xyz=ϕ ........(2)Where ϕ is a constant, it may be regarded as a function of x.
Differentiating (2) w.r.t. x , y, and z we get,
(xy2dx+yx2dy)+(xz2dx+zx2dz)−(yzdx+xzdy+xydz)=dϕ
On simplifying, we get
(yx2−xz)dy+(zx2−xy)dz+yzdx+(xy2+xz2−2yz)dx=dϕ ...........(3)
Since ,yzdx+(yx2−xz)dy+(zx2−xy)dz=0 (given equation) ,therefore equation (3) is,
(xy2+xz2−2yz)dx=dϕ ........(4)
Again from equation (2),
2x2y2+2x2z2−xyz=ϕ⟹ x2y2+x2z2−2xyz=2ϕ
Now dividing both side by x ,we get
⟹ xy2+xz2−2yz=x2ϕ............(5)
From equation (4) and (5) ,we get
x2ϕdx=dϕ⟹ x2dx=ϕdϕOn integrating ,we get
logx2+logk=logϕ
Where k is a constant.
⟹ log(x2k)=logϕ
⟹ x2k=ϕ
Now ,putting the value of ϕ in equation (2) ,we get
2x2y2+2x2z2−xyz=x2k⟹ xy2+xz2−2yz=2xk
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