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Determine for what number [tex]\( x \)[/tex], if any, the following function [tex]\( f(x) \)[/tex] is discontinuous.

[tex]\[ f(x) = \left\{\begin{array}{ll}
x + 2 & \text{if } x \leq 0 \\
2 & \text{if } 0 \ \textless \ x \leq 1 \\
x^2 + 2 & \text{if } x \ \textgreater \ 1
\end{array}\right. \][/tex]


Sagot :

To determine the points at which the given piecewise function [tex]\( f(x) \)[/tex] is discontinuous, we need to check the continuity at the boundaries of the piecewise intervals.

The function [tex]\( f(x) \)[/tex] is defined as follows:
[tex]\[ f(x) = \begin{cases} x + 2 & \text{if } x \leq 0 \\ 2 & \text{if } 0 < x \leq 1 \\ x^2 + 2 & \text{if } x > 1 \end{cases} \][/tex]

The boundaries of the intervals are at [tex]\( x = 0 \)[/tex] and [tex]\( x = 1 \)[/tex]. We'll check for continuity at these points by verifying if the left-hand limit, right-hand limit, and the function value at these points match.

### Check at [tex]\( x = 0 \)[/tex]:
1. Left-hand limit as [tex]\( x \to 0^- \)[/tex]:
[tex]\[ \lim_{x \to 0^-} f(x) = \lim_{x \to 0^-} (x + 2) = 0 + 2 = 2 \][/tex]

2. Right-hand limit as [tex]\( x \to 0^+ \)[/tex]:
[tex]\[ \lim_{x \to 0^+} f(x) = \lim_{x \to 0^+} 2 = 2 \][/tex]

3. Function value at [tex]\( x = 0 \)[/tex]:
[tex]\[ f(0) = 0 + 2 = 2 \][/tex]

Since the left-hand limit, right-hand limit, and the function value at [tex]\( x = 0 \)[/tex] are all equal to 2, the function [tex]\( f(x) \)[/tex] is continuous at [tex]\( x = 0 \)[/tex].

### Check at [tex]\( x = 1 \)[/tex]:
1. Left-hand limit as [tex]\( x \to 1^- \)[/tex]:
[tex]\[ \lim_{x \to 1^-} f(x) = \lim_{x \to 1^-} 2 = 2 \][/tex]

2. Right-hand limit as [tex]\( x \to 1^+ \)[/tex]:
[tex]\[ \lim_{x \to 1^+} f(x) = \lim_{x \to 1^+} (x^2 + 2) = 1^2 + 2 = 1 + 2 = 3 \][/tex]

3. Function value at [tex]\( x = 1 \)[/tex]:
[tex]\[ f(1) = 2 \][/tex]

At [tex]\( x = 1 \)[/tex], the left-hand limit is 2, while the right-hand limit is 3. Since these limits are not equal, the function [tex]\( f(x) \)[/tex] is discontinuous at [tex]\( x = 1 \)[/tex].

### Conclusion:
The function [tex]\( f(x) \)[/tex] is discontinuous at [tex]\( x = 1 \)[/tex]. This is the only point among the boundaries of the piecewise function intervals where the function exhibits discontinuity.