Epsilon-Delta Proof for Continuity of f + 2g at x = a

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SUMMARY

The discussion centers on the application of the epsilon-delta definition of continuity to the function f + 2g at the point x = a, given that both f and g are continuous at that point. The user successfully applies the triangle inequality to express the difference |f(x) + 2g(x) - (f(a) + 2g(a))| as |f(x) - f(a)| + 2|g(x) - g(a)|. This manipulation is valid and confirms the continuity of the combined function at x = a.

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  • Epsilon-delta definition of continuity
  • Triangle inequality in real analysis
  • Properties of continuous functions
  • Basic function operations (addition and scalar multiplication)
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Students in calculus or real analysis, particularly those learning about continuity and proof techniques. This discussion is beneficial for anyone looking to strengthen their understanding of epsilon-delta proofs.

rudders93
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Homework Statement



Part of an [itex]\epsilon-\delta[/itex] proof about whether or not f + 2g is continuous at x = a provided that f and g are continuous at x = a

The Attempt at a Solution



I've got the proof (I hope), but I'm uncertain about whether I can do the following:

[itex]|f(x)+2g(x)-(f(a)+2g(a))| = |f(x)-f(a)+2g(x)-2g(a)| \leq |f(x)-f(a)| + 2|g(x)-g(a)|[/itex] using the triangle inequality.

Is that valid?

Thanks!
 
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