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JEE Mains · Maths · STD 12 - 1. relation and function

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

  1. A \(f(x)>0\) only for \(x \in[4, \infty)\)
  2. B \(f(x)<0\) only for \(x \in[-1,3)\)
  3. C \(\int_0^2 f(x) d x=-6\)
  4. D \(f(x)=0\) for finitely many values of \(x\).
Verified Solution

Answer & Solution

Correct Answer

(B) \(f(x)<0\) only for \(x \in[-1,3)\)

Step-by-step Solution

Detailed explanation

\(f(x)=[x]^2-[x]-6=([x]+2)([x]-3)\) (1) \(f(x)>0 \Rightarrow[x] \in(-\infty,-2) \cup(3, \infty)\) \(\Rightarrow x \in(-\infty,-2) \cup[4, \infty)\) (2) \(f(x)<0 \Rightarrow[x] \in(-2,3)\) \(\Rightarrow x \in[-1,3)\) option (2) is correct (3)…