# Thread: confused while trying to factor this

1. ## confused while trying to factor this

y^3-y^2+3y-3 is what im factoring

the book says the answer is (y-1)(y^2+3)

i dont know how it gets there

heres what i try to do:
(y^3-y^2)+(3y-3)
-y^2(y-1) + 3(y-1)

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

what am i doing wrong?
as usual, thanks for any help. this site really helps me out

2. Originally Posted by NecroWinter
y^3-y^2+3y-3 is what im factoring

the book says the answer is (y-1)(y^2+3)

i dont know how it gets there

heres what i try to do:
(y^3-y^2)+(3y-3)
-y^2(y-1) + 3(y-1) : the common factor for the first term should be y^2.

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

what am i doing wrong?
as usual, thanks for any help. this site really helps me out
Look at the line in red. You error is there.

$\displaystyle (y^3-y^2)+(3y-3)$

$\displaystyle =y^2(y-1)+3(y-1) = (y-1)(y^2+3)$

3. ok now that leads me to a new question

my book has me factoring out negative numbers as well sometimes, how do you know what youre supposed to do? is it just when a negative number is all the way to the left?

4. You can take a negative factor here as well.

$\displaystyle (y^3-y^2)+(3y-3)$

$\displaystyle =-y^2(-y+1)-3(-y+1) = (-y+1)(-y^2-3)$

$\displaystyle =(-y+1)(-y^2-3)$

$\displaystyle =-(y-1)[-(y^2+3)] = (y-1)(y^2+3)$

You can follow whichever way you think is convenient.

5. double posted by mistake..