Math Problem Statement

∫0−∞xe−6x2dx

Solution

To solve the integral 0xe6x2dx\int_0^\infty x e^{-6x^2} \, dx, we can use a standard method for integrals of this type, which involves recognizing it as a Gaussian integral, but with a modification due to the xx term in the integrand.

Steps:

  1. Substitution: Let u=6x2u = 6x^2, so that: du=12xdxorxdx=du12.du = 12x \, dx \quad \text{or} \quad x \, dx = \frac{du}{12}.

  2. Rewriting the Integral: The limits change as follows:

    • When x=0x = 0, u=0u = 0.
    • When x=x = \infty, u=u = \infty.

    Now, the integral becomes: 0xe6x2dx=0eudu12.\int_0^\infty x e^{-6x^2} \, dx = \int_0^\infty e^{-u} \frac{du}{12}.

  3. Simplifying: 1120eudu.\frac{1}{12} \int_0^\infty e^{-u} \, du.

  4. Solving the Integral: The integral 0eudu\int_0^\infty e^{-u} \, du is a standard exponential integral, and its value is 1.

    Therefore: 112×1=112.\frac{1}{12} \times 1 = \frac{1}{12}.

Final Answer:

0xe6x2dx=112.\int_0^\infty x e^{-6x^2} \, dx = \frac{1}{12}.

Would you like a more detailed explanation or help with another problem? Here are some related questions you might find interesting:

  1. What is the general method to solve integrals involving Gaussian functions?
  2. How do we apply substitution to integrals of this form?
  3. Can this method be generalized to integrals with different powers of xx?
  4. What is the relationship between Gaussian integrals and probability theory?
  5. How do you handle improper integrals like this one, with infinite limits?

Tip: When dealing with integrals of the form 0xeax2dx\int_0^\infty x e^{-ax^2} \, dx, always look for substitution methods or recognize it as a Gaussian integral with an additional linear term.

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Math Problem Analysis

Mathematical Concepts

Calculus
Gaussian Integrals
Substitution in Integrals

Formulas

∫0∞ e^(-u) du = 1

Theorems

Gaussian integral
Substitution method in integrals

Suitable Grade Level

College/Undergraduate