Author Topic: Factorising cubics (Read 1910 times) Tweet Share

Over9000 · « **on:** March 14, 2009, 08:08:07 pm »

Hi, I would like to know how to factorise cubics like $x^3 - 9x^2 +27x -22$ and then how to get that in T.P form?

TrueTears · « **Reply #1 on:** March 14, 2009, 08:15:11 pm »

You can not factorise this without using a calculator. (at least not in VCEland

)

Over9000 · « **Reply #2 on:** March 14, 2009, 08:18:26 pm »

Oh, kk

Flaming_Arrow · « **Reply #3 on:** March 14, 2009, 08:25:02 pm »

one way you could do it is by using differentiation, finding when m=0 subbing that x value into f(x) and thus in the tp form

Gloamglozer · « **Reply #4 on:** March 15, 2009, 11:21:32 am »

Can't you use the factor theorem to find a factor and then use long division to factorise it?

Flaming_Arrow · « **Reply #5 on:** March 15, 2009, 11:48:03 am »

Can't you use the factor theorem to find a factor and then use long division to factorise it?

in this case there isnt an exact factor, the factor is like 1.2 something

TrueTears · « **Reply #6 on:** March 15, 2009, 12:04:15 pm »

yeah in this case, even with a CAS calc you can not get an exact answer

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