AP Calculus BC : Continuity in Terms of Limits

Study concepts, example questions & explanations for AP Calculus BC

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Example Questions

Example Question #1 : Limits And Continuity


The graph above is a sketch of the function . For what intervals is  continuous?

Possible Answers:

Correct answer:


 For a function to be continuous at a point must exist and

This is true for all values of  except and .

Therefore, the interval of continuity is .

Example Question #2 : Limits And Continuity

Consider the piecewise function:  

What is ?

Possible Answers:

Limit does not exist.

Correct answer:

Limit does not exist.


The piecewise function


indicates that  is one when  is less than five, and is zero if the variable is greater than five.  At , there is a hole at the end of the split.  

The limit does not indicate whether we want to find the limit from the left or right, which means that it is necessary to check the limit from the left and right.  From the left to right, the limit approaches 1 as  approaches negative five.   From the right, the limit approaches zero as  approaches negative five.

Since the limits do not coincide, the limit does not exist for .

Example Question #1 : Continuity In Terms Of Limits

Consider the function .

Which of the following statements are true about this function? 




Possible Answers:

I and II

I and III

II only

III only

Correct answer:

I and II


For a function to be continuous at a particular point, the limit of the function at that point must be equal to the value of the function at that point. 

 First, notice that 

This means that the function is continuous everywhere.

Next, we must compute the limit. Factor and simplify f(x) to help with the calculation of the limit.


Thus, the limit as x approaches three exists and is equal to , so I and II are true statements. 

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