Continuity of a two-variable function

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SUMMARY

The discussion focuses on proving the continuity of a two-variable function, specifically addressing problems related to parts b and d of a homework assignment. The participant has identified a formula involving the norm of the function but is uncertain about its applicability. A key insight provided is to analyze the expression |(2x+y)³ + x² + y² / (x² + y²) - 1| by simplifying it and converting to polar coordinates, particularly as r approaches 0.

PREREQUISITES
  • Understanding of two-variable functions and their limits
  • Familiarity with polar coordinates in calculus
  • Knowledge of continuity criteria for functions
  • Experience with mathematical proofs and inequalities
NEXT STEPS
  • Study the concept of continuity in multivariable calculus
  • Learn how to convert Cartesian coordinates to polar coordinates
  • Explore the epsilon-delta definition of continuity
  • Practice simplifying complex expressions involving limits
USEFUL FOR

Students studying calculus, particularly those tackling multivariable functions and continuity proofs, as well as educators seeking to enhance their teaching methods in these topics.

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Homework Statement



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Homework Equations



My main problem is connected with b/ and d/. I found a formula involving the norm of the function, but I'm not sure if it's a good idea using it.

The Attempt at a Solution



I can prove that a function is not continuous by finding different values for x and y for which the limit at the point is approaching different values, but have no idea how to prove that it is continuous.
 
Last edited:
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Hint for (b): Look at

[tex]\left| \frac{(2x+y)^3+x^2+y^2}{x^2+y^2} - 1\right|[/tex]

Simplify it and change it to polar coordinates. Think about [itex]r\rightarrow 0[/itex].
 
Thank you
 

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