What is the definition of function continuity? How to judge whether a function is continuous?

What is the definition of function continuity? How to judge whether a function is continuous?


If the limit of a function at point x is equal to the value of the function at that point, then the function is continuous at that point. If x is any point in the domain, then the function is continuous
It is OK to determine the continuous derivative of the function. If it can be derivative, it is sure to be continuous
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