# Old guy helping daughter

• Oct 25th 2009, 02:36 PM
jonb
Old guy helping daughter
We have no book and I am trying to go through example problems. I probably need to get a book and learn this all over again. 50 years old no and not done this since 20 years old.

2xsquared-8x+2=0

(2x-2)(1x-1) gets me 4x in the middle when I multiply it through.

Is this the right way to approach this, did I do something silly?
• Oct 25th 2009, 02:39 PM
Matrim
Quote:

Originally Posted by jonb
We have no book and I am trying to go through example problems. I probably need to get a book and learn this all over again. 50 years old no and not done this since 20 years old.

2xsquared-8x+2=0

(2x-2)(1x-1) gets me 4x in the middle when I multiply it through.

Is this the right way to approach this, did I do something silly?

Since your factoring. I would think that you would factor a 2 out of the whole problem. I don't know what would go into 1 and add up to -4 though. So my post is basically useless.

Factor out a 2(x^2-4x+1)
• Oct 25th 2009, 02:44 PM
e^(i*pi)
Quote:

Originally Posted by Matrim
Since your factoring. I would think that you would factor a 2 out of the whole problem. I don't know what would go into 1 and add up to -4 though. So my post is basically useless.

Factor out a 2(x^2-4x+1)

That's because nothing does. You can tell if a quadratic has integer factors by looking at the discriminant, $\Delta$

[tex]\Delta = b^2-4ac = 16-(4)(1)(1) = 12[/tex]. As 12 is not a square number this does not have integer factors and your factorisation is as far as it goes although the 2 can be cancelled
• Oct 25th 2009, 02:53 PM
jonb
Got it.

Can anyone recommend a book to relearn all of this?

Thanks
• Oct 26th 2009, 12:46 AM
scorpion007
Quote:

Originally Posted by jonb
Got it.

Can anyone recommend a book to relearn all of this?

Thanks

Perhaps Amazon.com: Engineering Mathematics (9780831133276): K. A. Stroud, Dexter J. Booth: Books