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Question:

Determine the value of 'k' for which the following function is continuous at x=3: f(x) = (x+3)²/(x-3), x≠3; k, x=3

Solution:

Function f is continuous at a point a if the following conditions are satisfied.

  1. f(a) is defined
  2. limx→af(x) exists
  3. limx→af(x) = f(a)
    Now → limx→3(x+3)²/(x-3) = k
    so using L'hospital rule (differentiating on both sides i.e., denominator and numerator), we get
    2(x+3) = k
    Now substitute x=3 => k=12