Question
For what value of $ k$ is the following function continuous at $x = 2$
$f(x) = \begin{matrix} 2x + 1 & ; & x< 2 \\ k & ; & x = 2 \\ 3x - 1 & ; & x> 2 \end{matrix} $
$f(x) = \begin{matrix} 2x + 1 & ; & x< 2 \\ k & ; & x = 2 \\ 3x - 1 & ; & x> 2 \end{matrix} $
$\lim\limits_{h \rightarrow 0} f (2 -h) = f(2) = \lim\limits_{h \rightarrow 0} f(2 + h)$
Now,
$f (2 - h) = 2 (2 - h) + 1 = 5 - 2h$$\therefore \lim\limits_{h \rightarrow 0} f(2- h) = 5$
Also,
$f(2 + h) = 3(2 + h) -1 = 5 + 3h$$ \lim\limits_{h \rightarrow 0} f(2 + h) = 5$
So, for continuity
$f(2) = 5.$$\therefore k = 5.$
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