Solve the given initial-value problem. The DE is homogeneous. xy2dy/dx = y3 - x3; y(1) = 2.
Solution:
Given a homogenous differential equation, xy2 dy/dx = y3 - x3
xy2dy/dx = y3 - x3
dy/dx = (y3 - x3)/ xy2
dy/dx = [(y/x)3 - 1]/(y2/x2) --- (1)
Put y/x = v ⇒ y = xv
Differentiate w.r.t x
dy/dx = x.dv/dx + v
Equation (1) becomes,
⇒ dv/dx + v = (v3 - 1)/v2
⇒ dv/dx = [(v3 - 1)/v2] - v
⇒ dv/dx = (v3 - 1 - v3)/v2
v2. dv = -1/x.dx
Integrate on both sides, we get
∫v2. dv = ∫-1/x.dx
v3/3 = -logx + C
[1/3(y3/x3)] + log x = C --- (2)
Now, given that y(1) = 2
Substituting y = 2 and x = 1 in equation(2)
[(1/3) × (23/13)]+ log 1 = C
C = 8/3
From equation (2), we get
⇒ (y3/3x3) + logx = 8/3
Therefore, the required differential equation is y3 + 3x3logx = 8x3.
Solve the given initial-value problem. The DE is homogeneous. xy2dy/dx = y3 - x3; y(1) = 2.
Summary:
The differential equation for the given initial-value problem xy2dy/dx = y3 - x3; y(1) = 1 is y3 + 3x3logx = 8x3.
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