When lim f(x) exists, it always equals f(a). State whether this statement is true or false.

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Understand the Problem

The question asks whether the statement about the limit of a function equaling the function's value at a point is true or false. It provides four answer options that reflect different interpretations of limit behavior.

Answer

B. False. The limit can never exist if $f(a)$ is not defined.
Answer for screen readers

B. False. The limit can never exist if $f(a)$ is not defined.

Steps to Solve

  1. Understanding the limit concept The statement involves the limit of a function as $x$ approaches $a$, expressed as $\lim_{{x \to a}} f(x)$. For the limit to exist and equal to $f(a)$, $f(a)$ must be defined and continuous at $a$.

  2. Identifying the conditions for limit equality For $\lim_{{x \to a}} f(x) = f(a)$ to be true, the following must hold:

    • $f(a)$ is defined (i.e., $f(a)$ exists).
    • The function $f(x)$ must approach the same value from both the left and right as $x$ approaches $a$.
  3. Analyzing the answer options Option A suggests that evaluating $f(x)$ at $x = a$ ensures the limit equals $f(a)$; however, this only holds if $f(a)$ is defined.

    Option B states that the limit cannot exist if $f(a)$ is not defined. This is true but doesn't address the limit existing even when $f(a)$ is defined.

    Option C correctly states that the limit depends on values near $a$, but does not directly address limit equality with $f(a)$.

    Option D emphasizes that if $x = a$, then $f(x) = f(a)$; this can be misleading unless $f(a)$ is defined.

  4. Conclusion based on definitions The statement is false in general because the limit does not always equal the function value at that point unless specified conditions are met.

B. False. The limit can never exist if $f(a)$ is not defined.

More Information

The statement that $\lim_{{x \to a}} f(x) = f(a)$ is a condition of continuity. A function is continuous at a point $a$ if the limit exists, equals the function value at that point, and $f(a)$ is defined.

Tips

A common mistake is to assume that if a limit exists, it must automatically equal the function's value at that point, ignoring the necessity for $f(a)$ to be defined.

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