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Multiple Choice
Which of the following explains why a function is discontinuous at ?
A
The limit of as approaches does not exist.
B
The limit of as approaches exists, but is not equal to .
C
is not defined.
D
is defined and the limit of as approaches equals .
Verified step by step guidance
1
Step 1: Recall the definition of continuity at a point x = a. A function f(x) is continuous at x = a if the following three conditions are satisfied: (1) f(a) is defined, (2) the limit of f(x) as x approaches a exists, and (3) the limit of f(x) as x approaches a is equal to f(a).
Step 2: Analyze the first condition: f(a) must be defined. If f(a) is not defined, the function is automatically discontinuous at x = a.
Step 3: Analyze the second condition: The limit of f(x) as x approaches a must exist. If the left-hand limit (as x approaches a from the left) and the right-hand limit (as x approaches a from the right) are not equal, the limit does not exist, and the function is discontinuous at x = a.
Step 4: Analyze the third condition: The limit of f(x) as x approaches a must equal f(a). If the limit exists but is not equal to f(a), the function is discontinuous at x = a.
Step 5: Summarize the reasons for discontinuity: A function f(x) is discontinuous at x = a if (1) f(a) is not defined, (2) the limit of f(x) as x approaches a does not exist, or (3) the limit exists but is not equal to f(a).