Math Problem Statement

Evaluate the integral \( \int x^2 \cdot \sqrt[3]{1 + x^3} \, dx \).

Solution

The integral in the uploaded image is:

x21+x33dx\int x^2 \cdot \sqrt[3]{1 + x^3} \, dx

Solution:

We'll solve this integral by using substitution:

  1. Substitute: Let u=1+x3u = 1 + x^3.
    Then, du=3x2dxdu = 3x^2 \, dx, or equivalently x2dx=du3x^2 \, dx = \frac{du}{3}.

  2. Rewrite the integral: Substituting uu and dudu into the integral: [ \int x^2 \cdot \sqrt[3]{1 + x^3} , dx = \int \sqrt[3]{u} \cdot \frac{du}{3}. ]

    Simplify the constant: 13u1/3du.\frac{1}{3} \int u^{1/3} \, du.

  3. Integrate: The antiderivative of u1/3u^{1/3} is: u1/3du=u4/34/3=34u4/3.\int u^{1/3} \, du = \frac{u^{4/3}}{4/3} = \frac{3}{4} u^{4/3}.

    Therefore: 13u1/3du=1334u4/3=14u4/3.\frac{1}{3} \int u^{1/3} \, du = \frac{1}{3} \cdot \frac{3}{4} u^{4/3} = \frac{1}{4} u^{4/3}.

  4. Back-substitute u=1+x3u = 1 + x^3: 14u4/3=14(1+x3)4/3.\frac{1}{4} u^{4/3} = \frac{1}{4} (1 + x^3)^{4/3}.

  5. Final answer: x21+x33dx=14(1+x3)4/3+C,\int x^2 \cdot \sqrt[3]{1 + x^3} \, dx = \frac{1}{4} (1 + x^3)^{4/3} + C, where CC is the constant of integration.


Do you want a detailed explanation of any of these steps?

Related Questions:

  1. What are the conditions for applying substitution in an integral?
  2. How do you handle integrals with cube roots or other fractional exponents?
  3. Can this integral be solved using any other techniques (e.g., by parts)?
  4. What is the geometric interpretation of the solution of this integral?
  5. How does this technique generalize for integrals of the form xn1+xkmx^n \cdot \sqrt[m]{1 + x^k}?

Tip:

When using substitution, always check that the differential dudu matches all terms in the integral to avoid mistakes.

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Math Problem Analysis

Mathematical Concepts

Integral Calculus
Substitution Method

Formulas

Substitution: Let \( u = f(x) \), then \( du = f'(x)dx \).
Integration of powers: \( \int x^n \, dx = \frac{x^{n+1}}{n+1} + C \), for \( n \neq -1 \).

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Undergraduate Calculus or Advanced High School