Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 294

Hey, I just have a question concerning associativity :

I have :

by associativityAnd I needed to prove each of my steps concerning an exercise. What I found weird was in the correction part, they justify the retreat of parentheses by saying "associativty" I thought that associativity was only used when you needed to add parentheses, or it can go in both ways ? Could anyone confirm it ???

Offline

**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 294

No, it is exactly the way I've put it in my first post ^^

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,471

hi Al-Allo

The rule for associativity is:

Nehushtan is absolutely right; associativity applies to binary operations; that is to say, two elements combined to make one; so a four element expression doesn't exist.

I assume that the questioner intends the four element expression means 'add' elements in pairs in order going left to right hence

combine a + b, then the result with c; then that result with d. This is what Nehushtan has written.

So how do you do it?

treat (a + b) as P; c as Q; d as R

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

Pages: **1**