Factor by grouping

• Oct 11th 2008, 07:45 AM
vikings20081983
Factor by grouping
Cant seem to figure this out. Any ideas or tips? Thanks for the help
• Oct 11th 2008, 08:08 AM
Banach
Hi! 1 is a root of your polynomial, so by polynomial long division you can find out the factors.
• Oct 11th 2008, 08:10 AM
Banach
-1 is also a root (one checks this by trying the factors of the constant coefficient -1).
• Oct 11th 2008, 08:37 AM
vikings20081983
So if Im getting the answer of C is that wrong?
• Oct 11th 2008, 09:55 AM
Banach
Of course that is wrong, C neither has the root 1 nor the root -1.
• Oct 11th 2008, 12:17 PM
vikings20081983
Ok I redid it and think I got the right answer, I first took

2x^3 + x^2 - 2x - 1

(2x^3 + x^2) - (2x - 1)

x^2( 2x + 1) + 1(2x + 1) found the common factor(not sure if thats the right term)

So my final answer would be

(2x + 1)(x^2 +1) Again this is factoring by grouping so if anyone has any input thanks
• Oct 11th 2008, 12:44 PM
Banach
It is not right, for the same reason as in the previous post. The - in the second row should be a plus, then it will work out. But the method is right and effective.
• Oct 11th 2008, 12:57 PM
vikings20081983
Dangit, Ok Ill try doing this again, just not getting it(Angry)