Solve the Differential Equation. Use the Fact that the given Equation is Homogeneous. dy/dx = (x2 + 8y2) / 3xy
We will be solving this by using the first-order separable ordinary differential equation.
Answer: The general solution of differential equation dy/dx = (x2 + 8y2) / 3xy is y = ± √c1x16/3 - x2/5
Let's solve this step by step.
Explanation:
Given, differential equation: dy/dx = (x2 + 8y2) / 3xy
Divide the numerator and denominator by x2 in the RHS
dy/dx = (1 + 8y2/x2) / 3(y/x) --------------- (1)
Let, y/x = v ----------- (2)
⇒ y = xv
Differentiating with respect to 'x' we get,
⇒ dy/dx = v + x dv/dx ------------- (3)
Substitue the values of (2) and (3) in (1):
⇒ v + x dv/dx = (1 + 8v2) / 3v
⇒ 3v2 + 3vx dv/dx = (1 + 8v2)
⇒ 3vx dv/dx = (1 + 5v2)
⇒ 3v dv / (1 + 5v2) = dx / x
Integrate on both sides:
∫ 3v dv /(1 + 5v2) = ∫ dx / x ---------------- (4)
Let z = 1 + 5v2
⇒ dz/dv = 10v
⇒ dv = dz/10v
Substitue the value of dv in (4)
∫ (3v/z) (dz/10v) = ∫ dx / x
∫ 3 dz /10z = ∫ dx / x
⇒ 3/10 ln(z) = ln (xc)
⇒ ln(z) = 10/3 ln(xc)
Substitue z = 1 + 5v2
ln(1 + 5v2) = ln(xc)10/3
ln(1 + 5(y/x)2) = ln(xc)10/3 [Since, v = y / x]
⇒ 1 + 5(y/x)2 = (xc)10/3
⇒ (y/x)2 = (1/5)cx10/3 - 1/5
⇒ y2 = (1/5)cx10/3 . x2 - x2/5
⇒ y2 = (1/5)cx16/3 - x2/5
⇒ y = ± √(1/5)cx16/3 - x2/5
⇒ y = ± √c1x16/3 - x2/5
Thus, the general solution of differential equation dy/dx = (x2 + 8y2) / 3xy is y = ± √c1x16/3 - x2/5
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