Thread: Please help Factor by grouping problem

Tried posting this elsewhere but running out of time

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 this which is wrong, anyone got a solution?

(2x + 1)(x^2 +1)

now factor it ...

You have the right idea. However, when you get to this point:

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

you need to factor out a (-1) from the right hand terms. Then you will get:

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

Therefore your answer is:

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

which can also be written as:

(x + 1)(x - 1)(2x + 1). So (A) would be your answer.