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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. Hii use long division. It's easy because you have the factor as x-2 and the cubic equation

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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.. )
First of all, the expression is quartic, so you have somehow managed to increase the order

Secondly, even if you change the exponents to and in place of and respectively, you have still not factored correctly.

Long division is one option, but inspection (or synthetic division) would be quicker. By inspection I basically mean comparing coefficients, except you don't necessarily have to write it out formally.

What you should end up with is: , after which you only have to factor a quadratic.

Note: where I suspect you are tripping up in the factorisation is that if you consider the coefficient of , on the right-hand side you get where you have correctly identified a = 6, i.e. you are left with not as you have it.
4. get the silver casio calculator
factorises cubics and quadratics, can intergrate with limits (good for checking), tis beast
5. (Original post by yoitsro)
get the silver casio calculator
factorises cubics and quadratics, can intergrate with limits (good for checking), tis beast
For shame!

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Updated: April 22, 2013
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