Comparison test on second species integrals

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SUMMARY

The discussion focuses on determining the convergence of the integral \(\int^{1}_{0} \frac{1}{1-x^{4}} dx\) using the Comparison Test. The user initially compares the function \(f(x) = \frac{1}{1-x^{4}}\) with \(g(x) = \frac{1}{1-x}\), concluding that since \(g(x)\) is divergent, \(f(x)\) must also be divergent. However, the correct approach is to find a divergent integral that is less than \(f(x)\), not greater. The hint provided emphasizes factoring \(1-x\) out of \(1-x^{4}\) to facilitate the comparison.

PREREQUISITES
  • Understanding of integral calculus, specifically convergence and divergence of integrals.
  • Familiarity with the Comparison Test for integrals.
  • Knowledge of function behavior near singularities, particularly at \(x = 1\).
  • Ability to manipulate algebraic expressions, such as factoring polynomials.
NEXT STEPS
  • Study the Comparison Test in detail, focusing on its application to improper integrals.
  • Learn how to factor polynomials and analyze their limits, particularly for functions like \(1-x^{4}\).
  • Explore examples of convergent and divergent integrals to solidify understanding.
  • Investigate other convergence tests, such as the Limit Comparison Test and the Ratio Test.
USEFUL FOR

This discussion is beneficial for students and educators in calculus, particularly those focusing on integral convergence, as well as mathematicians seeking to deepen their understanding of the Comparison Test.

Rono
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Homework Statement


Determine if the following integrals are convergent or divergent. Explain why.

\int^{1}_{0} \frac{1}{1-x^{4}} dx

The Attempt at a Solution


I've tried using Comparison Test, using f(x) = \frac{1}{1-x^{4}} and\; g(x) = \frac{1}{1-x}, 0 \leq f(x)\leq g(x) in ] 0,1 [ and I know g(x) is divergent. My question is if its plausible that, by using Comparison Test, if g(x) is divergent, will f(x) be divergent too?
 
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No. Not plausible. You want a divergent integral that's less than f(x), not greater. Hint: factor 1-x out of (1-x^4).
 
It was my first thought, but I considered it too simple to be true, thanks!
 

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