Mastering Definite Integrals for Solving Tricky Problems

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Homework Help Overview

The discussion revolves around the integration of the function \(\int_{0}^{1}\sqrt{\frac{4x^2-4x+1}{x^2-x+3}}dx\), focusing on techniques for evaluating definite integrals, particularly through substitution and manipulation of the integrand.

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts a substitution method, letting \(u=x^2-x+3\), but expresses confusion regarding the limits of integration and the evaluation of the resulting integral. Other participants suggest completing the square in both the numerator and denominator, and using a substitution for the radicand, although one participant questions the necessity of this approach.

Discussion Status

The discussion is ongoing, with some participants providing guidance on potential methods for simplifying the integral. The original poster has acknowledged confusion but has also indicated a clearer understanding after receiving feedback.

Contextual Notes

There is mention of changing limits of integration, which has contributed to the original poster's confusion. The discussion includes considerations of the absolute value of expressions within the integral, particularly around the point where \(2x-1\) changes sign.

sinClair
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Homework Statement


Integrate \int_{0}^{1}\sqrt{\frac{4x^2-4x+1}{x^2-x+3}}dx

Homework Equations

The Attempt at a Solution


U sub: let u=x^2-x+3 Then du=2x-1 and then have to evaluate \int_{3}^{3}\sqrt{\frac{du^2}{u}}dx But how with these limits of integration should this be 0? Not sure how to evaluate this...
 
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Complete the square in both numerator and denominator, then use a u-sub for the radican.
 
rocophysics said:
Complete the square in both numerator and denominator, then use a u-sub for the radican.
I see no reason to do that.

sinClair said:

Homework Statement


Integrate \int_{0}^{1}\sqrt{\frac{4x^2-4x+1}{x^2-x+3}}dx


Homework Equations




The Attempt at a Solution


U sub: let u=x^2-x+3 Then du=2x-1 and then have to evaluate \int_{3}^{3}\sqrt{\frac{du^2}{u}}dx But how with these limits of integration should this be 0? Not sure how to evaluate this...
\sqrt{x^2}= |x| and 2x- 1 changes sign at x= 1/2. This integral is the same as
\int_0^1 \frac{|2x-1|}{\sqrt{x^2- x+ 3}}dx= -\int_0^{1/2}\frac{2x-1}{\sqrt{x^2-x+ 3}}dx+ \int_{1/2}^1 \frac{2x-1}{\sqrt{x^2- x+ 3}}dx
 
Thank you so much. I was getting confused with changing the limits of integration back and forth but got it now, thanks.
 

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