MCQ
If $f(x) = \left\{ {\begin{array}{*{20}{c}}{\frac{{{x^2} - 9}}{{x - 3}}\,,}&{{\rm{if \,\,}}x \ne 3}\\{2x + k\,,}&{{\rm{otherwise}}}\end{array}} \right.$, is continuous at $x = 3,$ then $k = $
  • A
    $3$
  • $0$
  • C
    $-6$
  • D
    $1/6$

Answer

Correct option: B.
$0$
b
(b) $\mathop {\lim }\limits_{x \to 3} f(x) = \mathop {\lim }\limits_{x \to 3} \frac{{{x^2} - 9}}{{x - 3}} = \mathop {\lim }\limits_{x \to 3} (x + 3) = 6$

and $f(3) = 2(3) + k = 6 + k$

$\because  f $ is continuous at $x = 3$; 

$\therefore  $ $6 + k = 6 \Rightarrow k = 0$.

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