Answer:
y = x*sqrt(Cx - 1)
Step-by-step explanation:
Given:
dy / dx = (x^2 + 5y^2) / 2xy
Find:
Solve the given ODE by using appropriate substitution.
Solution:
- Rewrite the given ODE:
dy/dx = 0.5(x/y) + 2.5(y/x)
- use substitution y = x*v(x)
dy/dx = v + x*dv/dx
- Combine the two equations:
v + x*dv/dx = 0.5*(1/v) + 2.5*v
x*dv/dx = 0.5*(1/v) + 1.5*v
x*dv/dx = (v^2 + 1) / 2v
-Separate variables:
(2v.dv / (v^2 + 1) = dx / x
- Integrate both sides:
Ln (v^2 + 1) = Ln(x) + C
v^2 + 1 = Cx
v = sqrt(Cx - 1)
- Back substitution:
(y/x) = sqrt(Cx - 1)
y = x*sqrt(Cx - 1)
The volume of the original cylinder is
... V = π·r²·h
For r=1 and h=1, this is
... V = π·1²·1 = π
For the new cylinder, the volume is 1.089 times that amount.
... V = 1.089π = π·1.1²·(1-k)
... 1.089/1.21 = 1-k
... k = 1 - 1.089/1.21 = 1 - 0.9 = 0.1 = 10%
The appropriate choice is (B) 10.
The equation has no solution
