Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I've just started studying for an A-Level in Mathematics. This is probably a simple question but when I factorized the quadratic equation


I took out the common factor $3$ to get

$3(5x^2 + 14x - 3)$

Then factorized as follows:

$3(5x^2 - 1x + 15x - 1) = \\ 3(x(5x -1) + 3(5x - 1)) = \\ 3(x+3)(5x-1).$

When I checked the answer it was


My question is this answer the same as the one I arrived to but with a different arrangement, or was my answer simply wrong?

This is my first question on so I apologize in advance if I'm no adhering to the site's rules, e.g. what not to ask on the site.

share|cite|improve this question
Your answer is fine! Remember that the unknowns in the parentheses represent numbers, and we know that the order of multiplication does not matter. $2\times 3=3\times 2$ and so forth. – Andrew Nov 12 '12 at 4:32
3(x+3)(5x−1) = 3(5x−1)(x+3) – Eric Angle Nov 12 '12 at 4:32
Wow, you got a 100 points without even asking a question. I asked 28 and only got 100. But to answer your question the arrangements doesn't matter. What you did was right! – Q.matin Nov 12 '12 at 4:33
Thanks guys I just wanted to make sure. – Taurayi Nov 12 '12 at 4:34
@Q.matin Association Bonus because I have an account on where I have 2200+ points. – Taurayi Nov 12 '12 at 4:38
up vote 0 down vote accepted

Yes the answer is the same if you work in a classical set of numbers ($\mathbb R$ for example). (I suppose that since this concerne the A-level.) In that sets wa have : $a \times b = b \times a$ for all $a$ and $b$ in it. We say that: ' Multiplication is commutative in these sets'.

share|cite|improve this answer
I was going to wait for Andrew, but I guess you answered the question first, so I'll mark this as the answer to the question, thank you. – Taurayi Nov 12 '12 at 4:47
Thank you and good luck in your career in mathematics! – Mohamed Nov 12 '12 at 4:53

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.