Understanding Continuity in Functions: Quick FAQs

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SUMMARY

The discussion centers on the continuity of functions, specifically addressing the function f(x) = 1/x - 1/x + x, which is discontinuous at x=0 due to the undefined nature of 1/x at that point. It is established that while the sum of continuous functions results in a continuous function (f + g is continuous if f and g are continuous), the reverse is not necessarily true; the continuity of a function expressed as f = g + h does not imply that both g and h are continuous. An example provided illustrates this with g(x) being 1 for irrational x and 0 for rational x, demonstrating that g and h can be discontinuous while their sum remains continuous.

PREREQUISITES
  • Understanding of function continuity and discontinuity
  • Familiarity with mathematical functions and their definitions
  • Knowledge of rational and irrational numbers
  • Basic algebraic manipulation of functions
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  • Study the properties of continuous functions in calculus
  • Learn about the implications of the Intermediate Value Theorem
  • Explore examples of piecewise functions and their continuity
  • Investigate the concept of limits and their role in determining continuity
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Students of mathematics, educators teaching calculus, and anyone interested in the foundational concepts of function continuity and its implications in mathematical analysis.

jason177
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Lets say you have a function f(x)=1/x-1/x+x this function would still be discontinuous at x=0 even though the 1/x's would cancel, right? Also I know that combinations of continuous functions are also continuous, so for example if f and g are continuous then f+g is continuous. So my other question is: does that go both ways? so if you know that f=g+h is continuous does that imply that g and h are both continuous?
 
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it would be discontinuous at 0, since 1/x is not even defined at zero, so it wouldn't "make sense" to write f(0 ) if you had a 1/x term involved

if f = g+ h is continuous it certainly doesn't imply that g and h are continuous as well. For example, try g(x ) = 1 if x is irrational and g(x ) = 0 if x is rational -- then set h to be vice versa, g + h will be a constant function ( with the constant 1 ) but it is clear that neither g and h are continuous everywhere
 

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