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

$15x^2+42x-9$

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

$3(5x-1)(x+3)$

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 math.stackexchange.com so I apologize in advance if I'm no adhering to the site's rules, e.g. what not to ask on the site.

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    Found an error on line 7. You need to change 1 to a 3. The rules of this Web site don't let me edit your post because the edit would be less than 6 characters long.2013-09-02

1 Answers 1

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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'.

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    Thank you and good luck in your career in mathematics!2012-11-12