An interval that includes the end points.
Example: the interval [0,20] is all the numbers between 0 and 20, including 0 and 20.
Could also be written 0 ≤ x ≤ 20
Imagine a flight allows luggage "no more than 20 kg", so 20 kg is allowed, and 0 kg is allowed as that is simply no luggage: so 0 ≤ luggage ≤ 20 kg
Example: the interval [0,20] is all the numbers between 0 and 20, including 0 and 20.
Could also be written 0 ≤ x ≤ 20
Imagine a flight allows luggage "no more than 20 kg", so 20 kg is allowed, and 0 kg is allowed as that is simply no luggage: so 0 ≤ luggage ≤ 20 kg
See: Open Interval
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