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Question: Answered & Verified by Expert
If a function $f(x)$ defined on $[a, b]$ is discontinuous at $x=\alpha \in(a, b)$, then
MathematicsContinuity and DifferentiabilityAP EAMCETAP EAMCET 2023 (19 May Shift 1)
Options:
  • A $\lim _{x \rightarrow \alpha^{-}} f(x)=\lim _{x \rightarrow \alpha^{+}} f(x)=f(\alpha)$
  • B $\lim _{x \rightarrow \alpha^{+}} f(x) \neq f(\alpha)$
  • C $\lim _{x \rightarrow a^{-}} f(x)=f(a)$
  • D $\lim _{x \rightarrow b^{+}} f(x)=f(b)$
Solution:
2409 Upvotes Verified Answer
The correct answer is: $\lim _{x \rightarrow \alpha^{+}} f(x) \neq f(\alpha)$
$f(x)$ is defined on $[a, b]$ and discontinuous at $x=\alpha \in(a, b)$
Since $f(x)$ is discontinuous at $x=\alpha \in(a, b)$
Hence option (a) will never be true
but $\lim _{x \rightarrow \alpha} f(x) \neq f(\alpha)$ is showing that $f(x)$ is discontinuous
at $x=\alpha \in(a, b)$
Hence option (b) is correct.
Since function is not defined for $x \rightarrow a^{-}$. Hence option (c) is incorrect.
Since function is not defined when $x \rightarrow b^{+}$. Hence (d) is incorrect.

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