Math Problem Statement

Evaluate the integral \(\int_1^{\infty} \frac{x^2}{(x^3 + 2)^2} \, dx\).

Solution

The integral provided is:

1x2(x3+2)2dx\int_1^{\infty} \frac{x^2}{(x^3 + 2)^2} \, dx

Let's solve this step by step.

Step 1: Substitution

We will use a substitution to simplify the integrand. Let:

u=x3+2u = x^3 + 2

Then, the derivative of uu with respect to xx is:

dudx=3x2ordu=3x2dx\frac{du}{dx} = 3x^2 \quad \text{or} \quad du = 3x^2 \, dx

Thus, x2dx=du3x^2 \, dx = \frac{du}{3}.

Now, change the limits of integration. When x=1x = 1, u=13+2=3u = 1^3 + 2 = 3, and when xx \to \infty, uu \to \infty.

So the integral becomes:

313u2du\int_3^{\infty} \frac{1}{3u^2} \, du

Step 2: Simplify and Integrate

Now we can integrate this expression. The integral of u2u^{-2} is:

u2du=u1\int u^{-2} \, du = -u^{-1}

Therefore, the integral becomes:

13[1u]3\frac{1}{3} \left[ -\frac{1}{u} \right]_3^{\infty}

Step 3: Evaluate the Limits

Evaluating this at the limits:

13(1+13)=13×13=19\frac{1}{3} \left( -\frac{1}{\infty} + \frac{1}{3} \right) = \frac{1}{3} \times \frac{1}{3} = \frac{1}{9}

Final Answer:

1x2(x3+2)2dx=19\int_1^{\infty} \frac{x^2}{(x^3 + 2)^2} \, dx = \frac{1}{9}

Would you like more details or have any questions? Here are some related problems to practice:

  1. Evaluate 1x4(x5+1)2dx\int_1^{\infty} \frac{x^4}{(x^5 + 1)^2} \, dx.
  2. Solve 0dx(x2+1)2\int_0^{\infty} \frac{dx}{(x^2 + 1)^2}.
  3. Compute 1x(x2+1)2dx\int_1^{\infty} \frac{x}{(x^2 + 1)^2} \, dx.
  4. Find the value of 2dx(x3+4)2\int_2^{\infty} \frac{dx}{(x^3 + 4)^2}.
  5. Evaluate 01x2(x3+2)2dx\int_0^{1} \frac{x^2}{(x^3 + 2)^2} \, dx.

Tip: When solving improper integrals, always check if the integrand converges at infinity to ensure the integral has a finite value.

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Math Problem Analysis

Mathematical Concepts

Calculus
Improper Integrals
Substitution

Formulas

Substitution: u = x^3 + 2, du = 3x^2 dx
Integral of u^{-2}: \(\int u^{-2} \, du = -u^{-1}\)

Theorems

Improper Integral Convergence

Suitable Grade Level

University Level - Calculus