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Question 12

Let $$f(x)= [x]^{2}-[x+3]-3, x\in \mathbb R$$, where $$[\cdot]$$ is the greatest integer funtion. Then

$$f(x)=[x]^2-[x+3]-3$$

$$f(x)=[x]^2-[x]-6$$

$$=([x]-3)([x]+2)$$

$$f(x)=0 \text{ for } x \in[-2,1) \cup[3,4)$$

$$f(x)>0$$:

$$\Rightarrow([x]-3)([x]+2)>0$$

$$\Rightarrow[x] \in(-\infty,-2) \cup(3, \infty)$$

$$\Rightarrow x \in(-\infty,-2) \cup[4, \infty)$$

$$f(x)<0$$:

$$\Rightarrow x \in[-1,3)$$

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