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Really simple math time.

Name: Anonymous 2008-04-18 15:00

Ok I'm just doing factorisation of a quardratic expression of the form ax²+bx+c

And I've come across these two which I can't figure out what I'm supposed to do.

Factorise, where possible

7x²+47x+7

And

3x²+7xy+3y²

The book I have doesn't even have the answers for these in the back.

Name: Anonymous 2008-04-18 15:47

Can't be done.

Problem solved.

Name: Anonymous 2008-04-18 17:38

>>2
Thanks
Absolutly no factorisation possible?

Name: Anonymous 2008-04-18 17:48

First one doesn't have any nice factorizations, but you can use the quadratic formula to get the roots and then factor it, naturally. The second one is similar, but slightly different because of the presence of y. Pretend the y isn't there, and get the roots of 3x^2 + 7x + 3. Call these roots a and b. Then 3x^2 + 7xy + 3y^2 = 3(x - ay)(x - by).

Name: Anonymous 2008-04-18 18:57

Just use the quadratic formula for it all....else it's so much time waster guessing.

Name: Anonymous 2008-04-18 21:15

7x²+47x+7

=(14x + 47 + sqrt(2013))*(14x + 47 - sqrt(2013))/28

Name: Anonymous 2008-04-19 7:58

>>4
>>5
>>6

Thanks for the help guys.

Name: Anonymous 2008-04-19 22:34

ITT, people doing other people's homework

Name: Anonymous 2008-04-20 1:39

>>8
That's what /sci/ is for!

Name: Anonymous 2008-04-20 9:53

>>8
It isn't my homework. I'm a self studying A level student. So it's obviously difficult when I come across things I can't find an answer for.

Name: Anonymous 2008-04-20 11:49

actually the second one just seems like a (ax+by)² defactorization

Name: Anonymous 2008-04-20 12:02

3x²+7xy+3y²

so
3x² = a²x² -> a² = 3
3y² = b²y² -> b² = 3
7xy = 2abxy -> 2ab = 7

that's an impossible system, >>11, cause ab would be either 3 or -3, and in both cases, it's impossible for 6 = 7 or -6 = 7.

fail

unless you do it so that 7xy = 6xy + xy and then it'd be
3x² + 7xy + 3y² = 3(x+y)² + xy

Name: Anonymous 2008-04-20 12:04

>>4
learn with >>12

Name: Anonymous 2008-04-20 12:05

>>13
disregard that, I suck cocks
I meant the other way

Don't change these.
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