Continuity & Properties of functions

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SUMMARY

The discussion centers on proving that a continuous function f: R -> R, which approaches negative infinity as x approaches both positive and negative infinity, must have a maximum value on R. The proof involves using the definition of limits to establish that for any real number X, there exist bounds x1 and x2 such that f(x) is less than X for x greater than x1 and less than x2. The values of f(x) are then analyzed within the closed and bounded interval [x1, x2] to conclude the existence of a maximum value.

PREREQUISITES
  • Understanding of real-valued functions and their properties
  • Knowledge of limits and continuity in calculus
  • Familiarity with closed and bounded intervals in real analysis
  • Ability to apply the Extreme Value Theorem
NEXT STEPS
  • Study the Extreme Value Theorem and its implications for continuous functions
  • Learn about the properties of continuous functions on closed intervals
  • Explore the concept of limits at infinity in more depth
  • Review proofs involving continuity and boundedness in real analysis
USEFUL FOR

Students of calculus, mathematicians focusing on real analysis, and educators teaching properties of continuous functions will benefit from this discussion.

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Homework Statement



Let f:R->R be a continuous function where limit as x goes to positive/negative infinity is negative infinity. Prove that f has a maximum value on R.

Homework Equations


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The Attempt at a Solution


I tried to use the definition of infinite limits but I'm not sure how to do this explicitly.
 
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Let X be a real number. Since [itex]\lim_{x\rightarrow \infty}= -\infty[/itex], there exist x1[/sup] such that if x> x1, f(x)< X. Since [itex]\lim_{x\rightarrow -\infty}= -\infty[/itex], there exist x2 such that if x< x2, f(x)< X. Now look at the values of f(x) on the closed and bounded interval [x1, x2].
 

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