The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

How to factorise cubic expressions?

Ok so y = x^3 + x^2 - 2x

How do I do this :smile:

And x^3 - x^2

and x^3 = 9x


Basically I've used these questions because each one is different and uses different techniques :smile:

Thanks!!!! :biggrin:
Pull out common factors :smile:

Posted from the Bottom of the Big Blue Sea...
Reply 2
Avatar for Atheism
Atheism
8
Have you done remainder theorem? I.e. f(x)=x3+x2−2x f(x) =x^3 + x^2 -2x , when f(y)=0f(y)=0, (x-y) is a factor.
Original post by Atheism
Have you done remainder theorem? I.e. f(x)=x3+x2−2x f(x) =x^3 + x^2 -2x , when f(y)=0f(y)=0, (x-y) is a factor.


Thats the factor theorem :smile:

Posted from the Bottom of the Big Blue Sea...
Reply 4
Avatar for User995789
User995789
OP
14
Original post by shadab786ahmed
Pull out common factors :smile:

Posted from the Bottom of the Big Blue Sea...



Original post by Atheism
Have you done remainder theorem? I.e. f(x)=x3+x2−2x f(x) =x^3 + x^2 -2x , when f(y)=0f(y)=0, (x-y) is a factor.



Original post by shadab786ahmed
Thats the factor theorem :smile:

Posted from the Bottom of the Big Blue Sea...


No I haven't :s-smilie:
only x is a common factor????
Reply 5
Avatar for TenOfThem
TenOfThem
18
Original post by shadab786ahmed
Thats the factor theorem :smile:

Posted from the Bottom of the Big Blue Sea...


Sure, but the factor theorem is only a special case of the remainder theorem so it is the remainder theorem
Reply 6
Avatar for TenOfThem
TenOfThem
18
Original post by Blueray2
No I haven't :s-smilie:
only x is a common factor????


Then take x out and you have a quadratic to factorise
Reply 7
Avatar for User995789
User995789
OP
14
Original post by TenOfThem
Then take x out and you have a quadratic to factorise


oh so x(x^2+x-2)

then I solve x^2+x-2=0
to get 2 x brackets :smile:

and the first x is just = 0
Original post by TenOfThem
Sure, but the factor theorem is only a special case of the remainder theorem so it is the remainder theorem


That makes sense :tongue: :colondollar:

Posted from the Bottom of the Big Blue Sea...
Reply 9
Avatar for TenOfThem
TenOfThem
18
Original post by Blueray2
oh so x(x^2+x-2)

then I solve x^2+x-2=0
to get 2 x brackets :smile:

and the first x is just = 0


yes

remind me ... do you go to school and have a teacher or is this all you?
Reply 10
Avatar for User995789
User995789
OP
14
Original post by TenOfThem
Then take x out and you have a quadratic to factorise


Cheers I got it right :biggrin: Your amazing :colondollar:
Reply 11
Avatar for Goods
Goods
16
since everything is in terms of x it's much easier you just pull out x and then factorize the quadratic.
Reply 12
Avatar for User995789
User995789
OP
14
Original post by TenOfThem
yes

remind me ... do you go to school and have a teacher or is this all you?


I go school, but the teacher doesn't help, he refuses to, and I get loads of H.w
but it's fine I got it right with your help :smile:
Reply 13
Avatar for BabyMaths
BabyMaths
Original post by Blueray2
I go school, but the teacher doesn't help, he refuses to, and I get loads of H.w
but it's fine I got it right with your help :smile:


TenOfThem should be getting paid by your school as well as her own. :biggrin:
Original post by BabyMaths
TenOfThem should be getting paid by your school as well as her own. :biggrin:


LoL
Original post by TenOfThem
x


:eek: sorry! Didn't realise you were female :colondollar: I am on the app so cant see the signs!

Posted from the Bottom of the Big Blue Sea...
Reply 16
Avatar for User995789
User995789
OP
14
Original post by BabyMaths
TenOfThem should be getting paid by your school as well as her own. :biggrin:


:lol: I swear one day when I'm rich i'll make my own school which gives free tutoring :tongue:
Reply 17
Avatar for User995789
User995789
OP
14
Original post by BabyMaths
TenOfThem should be getting paid by your school as well as her own. :biggrin:



Original post by TenOfThem
LoL



Original post by shadab786ahmed
:eek: sorry! Didn't realise you were female :colondollar: I am on the app so cant see the signs!

Posted from the Bottom of the Big Blue Sea...


For the 2nd one I got
x^3 - x^2

= x(x^2-x)

what does (x^2-x) =
I mean in terms of x values to draw the sketchs :smile:
erm ....

x3−x2=x2(x−1)x^3-x^2 = x^2(x-1)
Reply 19
Avatar for User995789
User995789
OP
14
Original post by TenOfThem
erm ....

x3−x2=x2(x−1)x^3-x^2 = x^2(x-1)


lol yh my bad, was abt to edit that :smile:

Ok so x^2 = (x)(x)
so x = 0
and x =1
thanks I get it

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you