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GATE 2013 CS (CS1) – Question 32

Engineering Mathematics · Calculus · 1 mark · Multiple choice

Which function is continuous at x=3?

  1. f(3)=2; f(x)=x−1 for x>3; f(x)=(x+3)/3 for x<3
  2. f(3)=4; f(x)=8−x for x≠3
  3. f(x)=x+3 for x≤3; f(x)=x−4 for x>3
  4. f(x)=1/(x³−27) for x≠3

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Correct answer: (A) f(3)=2; f(x)=x−1 for x>3; f(x)=(x+3)/3 for x<3

Explanation

In A, the left limit is (3+3)/3=2 and the right limit is 3−1=2, both matching f(3)=2. B has limit five but value four. C has left/value six and right limit minus one. D is undefined and singular at three. Thus only A is continuous.

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