Guest

Greatest Integer Function

 

The function f(x) : R → Z defined as:

f(x) = [x] = greatest integer less than or equal to x is called the greatest integer function. The graph of a greatest integer function is shown in figure given below. The graph shows that it is increasing (not strictly) many-to-one function.

many-to-one-function

Illustration: Let [x + 1] = 3 then find x.

Solution:

From definition of greatest integer function

3 < x + 1 < 4

=> 2 < x < 3

Note:  Any number x can be written as

x = [x] + (x)

where [ ] denotes the integral part

and ( ) denotes the fractional part

i.e.

[3.7]  = 3

(3,7)  = 0.7

[-3,7] = -4

(-3.7) = 0.3.

Note:  0 < (x) < 1

∀ -2 < x < -1 => [x] = -2

∀ -1 < x < 0 => [x] = -1

∀ 0 < x < 1 => [x] = 0

∀ 1 < x < 2 => [x] = 1

∀ 2 < x < 3 => [x] =2

∀ n < x < n + 1 => [x] = n, n ε I

Examples

1. [x + 1] = [x] + 1 ∀ x ε R  True/False

2. |-(x/∏)| = -1-|x/∏|, x ≠ n ∏ , n ε I  True/False

3. If [(x) + x] = 3 then x =? where [ ] represents greatest integer function and  ( ) represents integer greater than or equal to x.

Ans.1  True

Ans.2  True

Ans.3 1 < x < 2

IIT JEE and AIEEE study material is available online free of cost at askIITians.com. Study Physics, Chemistry and Mathematics at askIITians website and be a winner. We offer numerous live online classroom courses as well for live online IIT JEE preparation - you do not need to travel anywhere any longer - just sit at your home and study for IIT JEE live online with askIITians.com

To read more, Buy study materials of Set Relations and Functions comprising study notes, revision notes, video lectures, previous year solved questions etc. Also browse for more study materials on Mathematics here.


TOP Your EXAMS!

Upto 50% Scholarship on Live Classes

Course Features

  • Video Lectures
  • Revision Notes
  • Previous Year Papers
  • Mind Map
  • Study Planner
  • NCERT Solutions
  • Discussion Forum
  • Test paper with Video Solution

r