PARENTHESIS if the number itself isn’t included

BRACKETS if the number itself is included

Parentheses, Braces, and Brackets in Math

🧠 When do you use which?

It depends on the context.

  1. When it says “from –3 to 3, inclusive
    → That means you want to include both ends.
    → Use [-3, 3].

  2. If it says “strictly between –3 and 3”
    → That means you don’t want –3 or 3 themselves.
    → Use (–3, 3).

  3. If you’re dealing with limits or discontinuities (like in Calculus (Main) or measure theory),
    → Excluding a point might matter (e.g., function undefined at 3, so you write [–3, 3)).