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.
-
When it says “from –3 to 3, inclusive”
→ That means you want to include both ends.
→ Use[-3, 3]
. -
If it says “strictly between –3 and 3”
→ That means you don’t want –3 or 3 themselves.
→ Use(–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)
).