Example of Continuous Function

Let’s take an example to find the continuity of a function at any given point.
Consider the function of the from

f\left(  x \right) = \left\{ {\begin{array}{*{20}{c}} {\frac{{{x^2} - 16}}{{x - 4}},\,\,\,if\,x \ne  4} \\ {0\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,,if\,x = 4} \end{array}}  \right.


We shall the check the of the given function at the point x = 4.
To check the continuity of the given function we follow the three steps.

(i) Value of Function at given Point:
We have given value of function at x =  4 is equal to 0.

f\left(  4 \right) = 0


(ii) Limit at a Function at given point:

\begin{gathered} \mathop {\lim }\limits_{x \to 4} f\left( x  \right) = \mathop {\lim }\limits_{x \to 4} \frac{{{x^2} - 16}}{{x - 4}} \\ \Rightarrow \mathop {\lim }\limits_{x \to 4}  f\left( x \right) = \mathop {\lim }\limits_{x \to 4} \frac{{{{\left( x  \right)}^2} - {{\left( 4 \right)}^2}}}{{x - 4}} \\ \Rightarrow \mathop {\lim }\limits_{x \to 4}  f\left( x \right) = \mathop {\lim }\limits_{x \to 4} \frac{{\left( {x + 4}  \right)\left( {x - 4} \right)}}{{x - 4}} \\ \Rightarrow \mathop {\lim }\limits_{x \to 4}  f\left( x \right) = \mathop {\lim }\limits_{x \to 4} \left( {x + 4} \right) \\ \end{gathered}


Applying the limits, we have

\Rightarrow  \mathop {\lim }\limits_{x \to 4} f\left( x \right) = 4 + 4 = 8


(iii) From the above it clear that

\mathop  {\lim }\limits_{x \to 4} f\left( x \right) \ne f\left( 4 \right)


Hence the function f is discontinues at the point x = 4.

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