Prove using the precise definition of the limit

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SUMMARY

The limit of the function as x approaches 2, expressed as lim x→2 (x² + 1) = 5, is established using the epsilon-delta definition of limits. The discussion highlights the critical steps in proving this limit, specifically the manipulation of the expression |x - 2| |x + 2| < ε. The solution requires ensuring that |x + 2| remains bounded away from zero as x approaches 2, which is essential for controlling the limit's behavior. The final conclusion emphasizes that by keeping x sufficiently close to 2, one can effectively manage the limit proof.

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Homework Statement



lim x→2 (x2+1) = 5

Homework Equations



0 < |x-a| < delta

|f(x) - L| < ε

The Attempt at a Solution



0 < |x-2| < delta

|x2-4| < ε

|(x-2) (x+2)| < ε

|x-2| |x+2| < ε.....and I am stuck here, any help
 
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TheRedDevil18 said:

Homework Statement



lim x→2 (x2+1) = 5

Homework Equations



0 < |x-a| < delta

|f(x) - L| < ε

The Attempt at a Solution



0 < |x-2| < delta

|x2-4| < ε

|(x-2) (x+2)| < ε

|x-2| |x+2| < ε.....and I am stuck here, any help

Continuing your analysis:$$
|x-2|<\frac \epsilon {|x+2|}$$You are trying to get the right side small by getting ##x## close to ##2##. So you don't want the denominator to get close to ##0##. Can you keep it away from ##0## if ##x## is close to ##2##? That's the idea you need to pursue.
 

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