Solve the separable differential equation dy/dx = xy.
Solution
Problem
Step 1: Recognize that the equation is separable.
The equation is:
dy/dx = xy
We can separate the variables so that all y-terms are on one side and all x-terms are on the other.
Step 2: Separate the variables for y ≠ 0.
Divide both sides by y and multiply by dx:
(1/y) dy = x dx
Step 3: Integrate both sides.
∫ (1/y) dy = ∫ x dx
This gives:
ln|y| = x^2/2 + C
Step 4: Solve for y.
Exponentiate both sides:
|y| = e^(x^2/2 + C)
Using e^(a + b) = e^a e^b:
|y| = e^C e^(x^2/2)
The arbitrary constant can absorb the sign and the factor e^C, so we write:
y = Ce^(x^2/2)
Step 5: Include the equilibrium solution.
During separation, we divided by y, so we should check y = 0 separately.
If y = 0, then dy/dx = 0 and xy = 0, so y = 0 is also a solution. It is included in y = Ce^(x^2/2) by taking C = 0.
Step 6: Check the general solution.
Differentiate:
y' = Cxe^(x^2/2)
Since y = Ce^(x^2/2):
y' = xy
Therefore, the general solution is y = Ce^(x^2/2).
Result
y = Ce^(x^2/2)