We are given a function $f(x) = \frac{1}{\lfloor 3x - 2 \rfloor}$, where $\lfloor x \rfloor$ denotes the greatest integer less than or equal to $x$. a) We need to find the domain $D_f$ of the function $f(x)$. b) We need to discuss the continuity of $f(x)$ at $x = 0$. The function is $f(x)$ and not $g(x)$. I will assume that it is $f(x)$ not $g(x)$

AnalysisDomainContinuityFloor FunctionLimits
2025/6/27

1. Problem Description

We are given a function f(x)=13x2f(x) = \frac{1}{\lfloor 3x - 2 \rfloor}, where x\lfloor x \rfloor denotes the greatest integer less than or equal to xx.
a) We need to find the domain DfD_f of the function f(x)f(x).
b) We need to discuss the continuity of f(x)f(x) at x=0x = 0. The function is f(x)f(x) and not g(x)g(x). I will assume that it is f(x)f(x) not g(x)g(x)

2. Solution Steps

a) Finding the domain of f(x)f(x):
The domain of f(x)f(x) consists of all real numbers xx for which the function is defined. Since we have a fraction, the denominator cannot be zero. Therefore, we require that 3x20\lfloor 3x - 2 \rfloor \neq 0.
This means that 03x2<10 \le 3x - 2 < 1 must be false. Thus, either 3x2<03x - 2 < 0 or 3x213x - 2 \ge 1.
3x2<03x - 2 < 0 implies 3x<23x < 2, so x<23x < \frac{2}{3}.
3x213x - 2 \ge 1 implies 3x33x \ge 3, so x1x \ge 1.
We want to find the values of xx for which 3x2=0\lfloor 3x - 2 \rfloor = 0.
This occurs when 03x2<10 \le 3x - 2 < 1.
Adding 2 to all sides, we get 23x<32 \le 3x < 3.
Dividing by 3, we get 23x<1\frac{2}{3} \le x < 1.
So, we need to exclude the interval [23,1)[\frac{2}{3}, 1) from the real numbers.
The domain of f(x)f(x) is therefore (,23)[1,)(-\infty, \frac{2}{3}) \cup [1, \infty).
b) Discussing the continuity of f(x)f(x) at x=0x = 0:
To check the continuity of f(x)f(x) at x=0x = 0, we need to evaluate limx0f(x)\lim_{x \to 0} f(x) and compare it with f(0)f(0).
First, let's find f(0)f(0):
f(0)=13(0)2=12=12=12f(0) = \frac{1}{\lfloor 3(0) - 2 \rfloor} = \frac{1}{\lfloor -2 \rfloor} = \frac{1}{-2} = -\frac{1}{2}.
Now, let's find the limit as xx approaches 0:
Since f(x)=13x2f(x) = \frac{1}{\lfloor 3x - 2 \rfloor}, we consider values of xx close to

0. For $x$ close to 0, $3x - 2$ is close to -

2. When $x$ is slightly greater than 0, $3x - 2$ is slightly greater than -2, so $\lfloor 3x - 2 \rfloor = -2$.

When xx is slightly less than 0, 3x23x - 2 is slightly less than -2, so 3x2=3\lfloor 3x - 2 \rfloor = -3.
Therefore, we need to check the left and right limits.
Right-hand limit:
limx0+f(x)=limx0+13x2=12+ϵ=12=12\lim_{x \to 0^+} f(x) = \lim_{x \to 0^+} \frac{1}{\lfloor 3x - 2 \rfloor} = \frac{1}{\lfloor -2 + \epsilon \rfloor} = \frac{1}{-2} = -\frac{1}{2} for small ϵ>0\epsilon > 0.
Left-hand limit:
limx0f(x)=limx013x2=12ϵ=13=13\lim_{x \to 0^-} f(x) = \lim_{x \to 0^-} \frac{1}{\lfloor 3x - 2 \rfloor} = \frac{1}{\lfloor -2 - \epsilon \rfloor} = \frac{1}{-3} = -\frac{1}{3} for small ϵ>0\epsilon > 0.
Since limx0+f(x)limx0f(x)\lim_{x \to 0^+} f(x) \neq \lim_{x \to 0^-} f(x), the limit limx0f(x)\lim_{x \to 0} f(x) does not exist.
Therefore, f(x)f(x) is discontinuous at x=0x = 0.

3. Final Answer

a) The domain of f(x)f(x) is (,23)[1,)(-\infty, \frac{2}{3}) \cup [1, \infty).
b) f(x)f(x) is discontinuous at x=0x = 0.

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