Please I need help for this questions on calculus 1

To Kouam, you have posted this as a Calculus I question but most of the content if from topology.
Tell us what definitions you are using.
For example, you use [imath]n\in\mathbb{N}[/imath] does tgat mean [imath]\mathbb{N}=\{0,1,2,3\cdots\}[/imath]? If not then what?
What does limit point mean? Be complete is in answering.
What does interior point mean? What does boundary point mean?
What is the closure of a set?
 
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