# Simultaneous equation

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• Sep 30th 2011, 07:28 AM
Quacky
Quacky's Guide to Factoring a Quadratic
Quote:

Originally Posted by andyboy179
so would i use 7 and 1, for example would i do 7x-1= -7 (i know that wouldn't fit but is it the correct way of doing it?)

You have 3 and 1.
You have 7 and 1.

-Take one number from the top and one number from the bottom.
-Pair them together and multiply them.
-There will be 2 numbers left unselected.
-Pair them together and multiply them.
-See if you can add them or subtract them to obtain 4
-If you can, place each paired number in an opposite bracket. You know which values are "stuck" to a $\displaystyle y$ so then you just need to work out the signs.
• Sep 30th 2011, 07:37 AM
andyboy179
Re: Quacky's Guide to Factoring a Quadratic
7-3=4 so that would be it and y= -7 or -3
• Sep 30th 2011, 07:39 AM
Quacky
Re: Quacky's Guide to Factoring a Quadratic
Quote:

Originally Posted by andyboy179
7-3=4 so that would be it and y= -7 or -3

We know it's $\displaystyle (3y\pm~)(y\mp~)$

Finish it up. Which numbers go in which brackets? Read through what I said above again if you get confused.
• Sep 30th 2011, 07:41 AM
andyboy179
Re: Quacky's Guide to Factoring a Quadratic
(3y+7) (y+3)???
• Sep 30th 2011, 09:11 AM
andyboy179
Re: Quacky's Guide to Factoring a Quadratic
actually it would be (3y - 7)(y + 1) = 0
y= 7/3 or -1
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