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**

**123ronnie321****Member**- Registered: 2010-09-28
- Posts: 128

Let V be a vector space and A,B be subsets of V .

prove that: span (A U B) = span (A) + span (B)

looks pretty obvious but dont know how to prove it using math

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,786

Hi 123ronnie321

I don't think that's true. Look at A={(1,0,0),(0,1,0)} and B={(1,0,0),(0,0,1)}, for example.

, on the other hand, is true.*Last edited by anonimnystefy (2013-02-25 18:14:28)*

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

Offline

**scientia****Member**- Registered: 2009-11-13
- Posts: 222

I think 123ronnie321 is looking for the direct sum, not the union.

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,786

Ah, I am sorry, then.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

Offline

Pages: **1**