Let [x] denote the greatest integer ≤ x, where x∈ R. If the domain of the real valued function f(x)=√ |[x]|-2 |[x]|-3 is (-∞ ,a)∪ [b,c)∪ [4,∞…
JEE Main 2021 — Mathematics Algebra
2021mcqmedium
Let [x] denote the greatest integer ≤x, where x∈R. If the domain of the real valued function f(x)=∣[x]∣−3∣[x]∣−2 is (−∞,a)∪[b,c)∪[4,∞),a<b<c, then the value of a+b+c is:
Official previous-year question
Held on 20 Jul 2021 · Verified 6 Jul 2026.
Options
A
8
B
1
C
−2
D
−3
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Solution
We have,f(x)=∣[x]∣−3∣[x]∣−2
For domain,
(∣[x]∣−3∣[x]∣−2)≥0
Case I: When ∣[x]∣−2≥0 and ∣[x]∣−3>0, then
∴x∈(−∞,−3)∪[4,∞)...(1)
Case II: When ∣[x]∣−2≤0 and ∣[x]∣−3<0, then
∴x∈[−2,3)...(2)
So, from (1) and (2), we get
Domain of function is
(−∞,−3)∪[−2,3)∪[4,∞)
∴(a+b+c)=−3+(−2)+3=−2
(∵a<b<c)
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