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# Factorising cubics watch

1. Oh the joys of additional maths...
I'm really confused on how to factorise cubics, they are new to me and well the teacher either didn't explain them amazingly or I zoned out.... So if this is the question, how would you factorise it?
6x³-13x²+x+2 is divided by (x-2). The remainder is 0, so I know that (x-2) is a factor. I also know you have to do this:-
(x-2) (6x³-13²+1) but how do I factorise the bracket with the cubic?
Thanks for any help.. )
2. (Original post by Phoebe♥)
Oh the joys of additional maths...
I'm really confused on how to factorise cubics, they are new to me and well the teacher either didn't explain them amazingly or I zoned out.... So if this is the question, how would you factorise it?
6x³-13x²+x+2 is divided by (x-2). The remainder is 0, so I know that (x-2) is a factor. I also know you have to do this:-
(x-2) (6x³-13²+1) but how do I factorise the bracket with the cubic?
Thanks for any help.. )
The problem is that you've written the second line wrong, if you multiply out the brackets you will see that you do not get the original cubic

Try long division
3. (Original post by Phoebe♥)
Oh the joys of additional maths...
I'm really confused on how to factorise cubics, they are new to me and well the teacher either didn't explain them amazingly or I zoned out.... So if this is the question, how would you factorise it?
6x³-13x²+x+2 is divided by (x-2). The remainder is 0, so I know that (x-2) is a factor. I also know you have to do this:-
(x-2) (6x³-13²+1) but how do I factorise the bracket with the cubic?
Thanks for any help.. )
You know one bracket (x-2) you just have to figure the rest

You need the to multiply with the x
You need the -1 to multiply with the -2

When you multiply -2 by you get and you will need another

SO the x multiplied by the ?x will give you that if ? is -1

So you have

You should know how to factorise a quadratic
4. you know that is a factor, so use the fact that:

expand the right side, and equate the coefficients of like powers.
5. (Original post by Phoebe♥)
Oh the joys of additional maths...
I'm really confused on how to factorise cubics, they are new to me and well the teacher either didn't explain them amazingly or I zoned out.... So if this is the question, how would you factorise it?
6x³-13x²+x+2 is divided by (x-2). The remainder is 0, so I know that (x-2) is a factor. I also know you have to do this:-
(x-2) (6x³-13²+1) but how do I factorise the bracket with the cubic?
Thanks for any help.. )
divide by

and then you will get a quadratic which you can factorize into the form
6. (Original post by upthegunners)
divide by
No

The other way round
7. (Original post by TenOfThem)
No

The other way round
haha yea

That's what I meant...past my bed time

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