Hi all - me again,

I have a math exam in the morning. Lucky for me, I have some past papers, and only the numbers, not the questions, change each year.

I was wondering if someone could help me with the solution I have here:

1

a) Fully factorize:

3x

-7x

-3x+7

The solution which I have been given is to first of all do this:

1 I...3...............-7............-3..........7

....I

....I_________3_____-4_____7_____

.......3............... -4............-7..........0

Which then goes onto this:

3x

- 4x -7 = (3x-7)(x+1)

so (x-1)(3x-7)(x+1)

Can someone please explain all of the above to me? I have no idea what the grid thing does, how the 4 gets in there? Basically, help? Please?

Cheers,

Martin