Math Problem Statement

Solve the integral \( \int \frac{\sqrt{x} + 2}{\sqrt{x} - 1} dx \)

Solution

The integral presented in the image is:

x+2x1dx\int \frac{\sqrt{x} + 2}{\sqrt{x} - 1} \, dx

Solution:

To solve this integral, we will simplify and decompose it:

  1. Let u=xu = \sqrt{x}, so x=u2x = u^2 and dx=2ududx = 2u \, du. Substituting into the integral:

    x+2x1dx=u+2u12udu\int \frac{\sqrt{x} + 2}{\sqrt{x} - 1} \, dx = \int \frac{u + 2}{u - 1} \cdot 2u \, du

    This simplifies to:

    2u(u+2)u1du2 \int \frac{u(u + 2)}{u - 1} \, du

  2. Expand and simplify the numerator:

    u(u+2)=u2+2uu(u + 2) = u^2 + 2u

    So the integral becomes:

    2u2+2uu1du2 \int \frac{u^2 + 2u}{u - 1} \, du

  3. Perform polynomial long division of u2+2uu1\frac{u^2 + 2u}{u - 1}:

    • Divide u2u^2 by uu: quotient is uu.
    • Multiply uu by (u1)(u - 1): result is u2uu^2 - u.
    • Subtract u2uu^2 - u from u2+2uu^2 + 2u: remainder is 3u3u.
    • Divide 3u3u by u1u - 1: quotient is 33, remainder is 33.

    Thus:

    u2+2uu1=u+3+3u1\frac{u^2 + 2u}{u - 1} = u + 3 + \frac{3}{u - 1}

    Substituting this back:

    2u2+2uu1du=2(u+3+3u1)du2 \int \frac{u^2 + 2u}{u - 1} \, du = 2 \int \left( u + 3 + \frac{3}{u - 1} \right) \, du

  4. Break the integral into parts:

    2udu+23du+23u1du2 \int u \, du + 2 \int 3 \, du + 2 \int \frac{3}{u - 1} \, du

    Solve each term:

    • 2udu=u2+C12 \int u \, du = u^2 + C_1
    • 23du=6u+C22 \int 3 \, du = 6u + C_2
    • 23u1du=6lnu1+C32 \int \frac{3}{u - 1} \, du = 6 \ln|u - 1| + C_3
  5. Combine the results:

    u2+6u+6lnu1+Cu^2 + 6u + 6 \ln|u - 1| + C

  6. Substitute back u=xu = \sqrt{x}:

    x2+6x+6lnx1+C\sqrt{x}^2 + 6\sqrt{x} + 6 \ln|\sqrt{x} - 1| + C

Final Answer:

x+6x+6lnx1+Cx + 6\sqrt{x} + 6 \ln|\sqrt{x} - 1| + C

Let me know if you'd like further clarification or additional steps! Here are 5 related questions for deeper exploration:


  1. How do you handle polynomial division in integrals?
  2. What substitution would be useful if x1\sqrt{x} - 1 had a power greater than 1 in the denominator?
  3. How does logarithmic integration arise in rational functions?
  4. What role does substitution play in simplifying square roots in integrals?
  5. Can this integral be solved using partial fractions instead of substitution?

Tip: Always check whether substitution or a direct approach simplifies an integral faster!

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Math Problem Analysis

Mathematical Concepts

Integration
Substitution
Polynomial Division
Logarithmic Integration

Formulas

Substitution: Let \( u = \sqrt{x} \), then \( x = u^2 \) and \( dx = 2u \, du \)
Polynomial Division: \( \frac{u^2 + 2u}{u - 1} = u + 3 + \frac{3}{u - 1} \)
Logarithmic Integration: \( \int \frac{1}{x} dx = \ln|x| + C \)

Theorems

Integration by Substitution
Logarithmic Rule of Integration

Suitable Grade Level

Undergraduate Calculus (or Advanced High School)