Question

Explain fully the concept of open and closed intervals.

Answer 1

It is written as (a,b). It means that x lies between a and b but does not include a or b, i.e. a;x;b.
If x lies in (5,10) then x can take values 6,7,8,9 but x cannot be 5 or 10.
Open interval does not include the end points.
Closed intervals:
It is written as [a,b]. It means that x lies between a and b including a and b, i.e. a;=x;=b.
If x lies in [5,10] then x can take values 5,6,7,8,9,10.
Closed interval includes the end points.