Consider the differential equation dy/dx = x^2(y - 1). Find the particular solution to this differential equation with initial condition f(0) = 3.

I got y = e^(x^3/3) + 2.

User Icon for Damon Damon answered
7 years ago

assuming that your answer is correct

dy/dx = x^2 e^(x^3/3)
but
e^(x^3/3) = y-2
so
dy/dx = x^2 (y-2) hummm

I'll try
dy/(y-1) = x^2 dx

ln(y-1)= x^3/3 + c

(y-1) = e^[x^3/3 + c]
y-1 = e^(x^3/3) e^c
y-1 = Ce^(x^3/3)
y = 1 + Ce^(x^3/3)

3 = 1 + C
C = 2

so
y = 1 + 2e^(x^3/3)

User Icon for Explain Bot Explain Bot answered
1 year ago

To find the particular solution to the given differential equation, we can separate the variables and then integrate both sides with respect to x.

Starting with the given differential equation: dy/dx = x^2(y - 1)

Separating the variables by bringing dy to one side and dx to the other side: (1/(y - 1))dy = x^2 dx

Now, we can integrate both sides. Integrating the left side involves using the natural logarithm function (ln), while integrating the right side involves using the power rule for integration.

∫(1/(y - 1))dy = ∫x^2 dx

To integrate 1/(y - 1) with respect to y, we can use the substitution u = y - 1. This gives us du = dy, and the integral becomes:

∫(1/u)du = ln|u|

Substituting back u = y - 1, we have:

ln|y - 1| = ∫x^2 dx

Integrating x^2 with respect to x gives us:

ln|y - 1| = (1/3)x^3 + C

Where C is the constant of integration.

Next, we can solve for y by exponentiating both sides:

|y - 1| = e^((1/3)x^3 + C)

To simplify the equation, we can remove the absolute value by considering two cases:

Case 1: y - 1 > 0, implies y > 1

In this case, we have:

y - 1 = e^((1/3)x^3 + C)

y = e^((1/3)x^3 + C) + 1

Case 2: y - 1 < 0, implies y < 1

In this case, we have:

-(y - 1) = e^((1/3)x^3 + C)

-y + 1 = e^((1/3)x^3 + C)

y - 1 = -e^((1/3)x^3 + C)

y = -e^((1/3)x^3 + C) + 1

So, the particular solution to the given differential equation with initial condition f(0) = 3 is:

y = e^(x^3/3) + 1 (since f(0) = 3 implies y > 1)

User Icon for Step-by-Step Bot Step-by-Step Bot answered
1 year ago

To find the particular solution to the given differential equation, we can follow these steps:

Step 1: Separate the variables.
Rewrite the given differential equation as:
dy / (y - 1) = x^2 dx.

Step 2: Integrate both sides.
Integrating both sides, we get:
∫ dy / (y - 1) = ∫ x^2 dx.

Step 3: Integrate the left side.
The integral of 1 / (y - 1) with respect to y is ln|y - 1|.
Therefore, the left side becomes ln|y - 1| + C1, where C1 is the constant of integration.

Step 4: Integrate the right side.
The integral of x^2 with respect to x is (1/3) x^3.
Therefore, the right side becomes (1/3) x^3 + C2, where C2 is the constant of integration.

Step 5: Apply the initial condition.
Substitute the initial condition f(0) = 3 into the equation.
ln|3 - 1| + C1 = (1/3) (0)^3 + C2.
Simplifying this equation, we have:
ln(2) + C1 = C2.

Step 6: Combine the constants.
Combine the constants C1 and C2 into a single constant C:
ln(2) + C1 = C.

Step 7: Solve for y.
Substituting the constants back into the equation, we get:
ln|y - 1| = (1/3) x^3 + ln(2) + C.

Exponentiating both sides, we have:
|y - 1| = e^((1/3) x^3 + ln(2) + C).

Since the absolute value can be positive or negative, we have two cases to consider:

Case 1: y - 1 > 0:
In this case, we can remove the absolute value:
y - 1 = e^((1/3) x^3 + ln(2) + C).

Case 2: y - 1 < 0:
In this case, we need to flip the sign:
-(y - 1) = e^((1/3) x^3 + ln(2) + C).
Simplifying, we get:
1 - y = e^((1/3) x^3 + ln(2) + C).

Step 8: Find y.
For Case 1: y - 1 = e^((1/3) x^3 + ln(2) + C).
Adding 1 to both sides, we have:
y = 1 + e^((1/3) x^3 + ln(2) + C).

For Case 2: 1 - y = e^((1/3) x^3 + ln(2) + C).
Subtracting 1 from both sides, we get:
-y = -1 + e^((1/3) x^3 + ln(2) + C).
Multiplying both sides by -1, we obtain:
y = 1 - e^((1/3) x^3 + ln(2) + C).

Therefore, the particular solution to the given differential equation with the initial condition f(0) = 3 is:
y = 1 + e^((1/3) x^3 + ln(2) + C).