What is the difference between a finite interval and an infinite interval?Which of the following intervals are finite and why? 1. ( a, ∞) ...

For instance, the first interval is finite on the left
side and infinite to the right
side.

Why?

Because, the left
end of the interval is a real number, since the right end is a symbol, and not a
value.

The real set of number contains also the symbols
infinite and -infinite, but they are not real values.

The
second interval (1, 1.4] is also finite, since both ends are real values. This interval
is opened to the left side and closed to the right. That means that the value 1 is not
included but is included. 

The 3rd interval
is the real set of numbers, that is
infinite.

(-∞ ,∞) =
R