Mom needs help teaching factoring  TOPIC_SOLVED

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Mom needs help teaching factoring

Postby kmillin on Thu Feb 06, 2014 5:45 am

My daughter has a problem that I cannot figure out how the teacher's book came up with the answer. They did not provide the intermediate step and there are several like this. If I can see how one is worked, I can figure out the other ones.. Here is the problem....Directions: Factor each polynomial completely.

49x^2 + 28square root of 3 + 12

The answer given is (7x + 2square root of 3)^2

I can get from the answer to the problem but what comes in between!!

Thanks for your help!

Kathy
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Re: Mom needs help teaching factoring

Postby maggiemagnet on Thu Feb 06, 2014 10:33 am

kmillin wrote:Directions: Factor each polynomial completely.

49x^2 + 28square root of 3 + 12

The answer given is (7x + 2square root of 3)^2

But that doesn't work: (7x + 2sqrt[3])^2 = (7x + 2sqrt[3])(7x + 2sqrt[3]) = (7x)(7x) + (7x)(2sqrt[3]) + (2sqrt[3])(7x) + (2sqrt[3])(2sqrt[3]) = 49x^2 + 28sqrt[3]x + 4*3. You'd need the middle term to have an x in it for the factoring to work that way.
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Re: Mom needs help teaching factoring  TOPIC_SOLVED

Postby kmillin on Thu Feb 06, 2014 2:49 pm

Could it be that the teacher's book is (gasp!)....wrong?? :shock: There are 4 problems with this format (x^2 + #sqrt# + # OR #x^2 + #sqrt# + #). It really has me baffled.....I keep wondering if we need to somehow deal with the last two factors since they are constants before we factor out the whole problem (but then I go back to....where does the x go? I understand your point about the 28sqrt3 x!

Thanks!
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