Question

I'm supposed to write the following intervals as sets indescriptive form:

a. (t, infinity), t a fixed real number

b. (0, 1/n), n a fixed natural number

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I think it is:
a. (t, infinity) = {x: t < x < infinity}
b. (0,1/n) = {x: 0 < x < 1/n}

Is this correct?
Also, how do you indicate that t is a fixed realnumber and n a fixed natural number?

Answer 1

Is correct.

Explanation:

If you don't write the n and t in the left part of the set (before the : ) we assume that are fixed.

(t, infinity) = {
`x \in \mathbb{R} : t<x<\infty, t\in \mathbb{R}`}

(0,1/n) = {
`x \in \mathbb{R} : 0<x<(1)/(n), n\in \mathbb{N}`}