Math Problem Statement

Find the indefinite integral of \( \int \frac{x}{\sqrt{8x^2 + 5}} \, dx \).

Solution

To solve this integral:

x8x2+5dx\int \frac{x}{\sqrt{8x^2 + 5}} \, dx

we can use a substitution method. Here’s the step-by-step process:

  1. Choose a substitution: Let u=8x2+5u = 8x^2 + 5. Then, du=16xdxdu = 16x \, dx, or equivalently, du16=xdx\frac{du}{16} = x \, dx.

  2. Rewrite the integral: Substitute u=8x2+5u = 8x^2 + 5 and xdx=du16x \, dx = \frac{du}{16}: x8x2+5dx=du16u=116u12du\int \frac{x}{\sqrt{8x^2 + 5}} \, dx = \int \frac{\frac{du}{16}}{\sqrt{u}} = \frac{1}{16} \int u^{-\frac{1}{2}} \, du

  3. Integrate with respect to uu: 116u12du=1162u12=18u\frac{1}{16} \int u^{-\frac{1}{2}} \, du = \frac{1}{16} \cdot 2 u^{\frac{1}{2}} = \frac{1}{8} \sqrt{u}

  4. Substitute back u=8x2+5u = 8x^2 + 5: 188x2+5\frac{1}{8} \sqrt{8x^2 + 5}

  5. Final Answer: x8x2+5dx=188x2+5+C\int \frac{x}{\sqrt{8x^2 + 5}} \, dx = \frac{1}{8} \sqrt{8x^2 + 5} + C

Let me know if you'd like further clarification on any steps!


Related Questions

  1. What are the steps to integrate functions using substitution?
  2. How do you determine which substitution to use for a given integral?
  3. Can trigonometric substitutions be used for integrals of this type?
  4. What is the difference between definite and indefinite integrals?
  5. How does integration relate to finding areas under curves?

Tip

When using substitution in integration, always remember to change both the integrand and the differential dxdx in terms of the new variable.

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Math Problem Analysis

Mathematical Concepts

Calculus
Integration
Substitution Method

Formulas

Integral of \( \int \frac{x}{\sqrt{ax^2 + b}} \, dx \) using substitution
Integral of \( \int u^{-1/2} \, du \)

Theorems

Substitution Rule for Integration

Suitable Grade Level

Undergraduate Calculus