Kaly A.

asked • 09/19/13

I am factoring quardratic trinomials. The problem I'm working with is the following: 12x2 + -46x + 42. How do I factor it?

I just need help factoring quadratic trinomials. Specifically 12x2 + -46x + 42.

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Parviz F. answered • 09/20/13

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Thomas E. answered • 09/19/13

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Kaly A.

Thank you! That was what I had been getting. But what I wasn't sure about was how to check it. Once you have 2(3x-7)(2x-3) then how do you get it to come out with 12x2 + -46x + 42? If I just take (3x-7)(2x-3) and use the FOIL method then it comes out with 6x2-23x+21. That of course is just half of 12x2 + -46x + 42. So obviously, if I used 2(3x-7)(2x-3) then it should come out with the right answer. I'm sure I'm making some stupid mistake while doing this, but apparently there's something I'm just not getting. To get 2(3x-7)(2x-3) to come back with 12x2 + -46x + 42, what do I do? What I was doing was starting out with 2 times 3x and 2 times 2x. Then multiply those together. But then that comes out with 24x2 when I need 12x2. So what do I do? Use the FOIL method and then multiply everything by 2?
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09/19/13

Denise W.

Yes, follow PEDMAS and multiply out the terms in the parentheses first.  You end up with 2[6x2 - 23x + 21] and then you just multiply each term in the parentheses by 2 to get 12x2 - 46x + 42.
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09/19/13

Ryan S. answered • 09/19/13

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Mathematics and Statistics

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