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#1 2007-06-02 19:29:54

mathsyperson
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Registered: 2005-06-22
Posts: 4,900

Solving cubic equations

This question was originally posted in someone else's topic so I moved it.

R3hall wrote:

Could someone here solve it algebraically with the formula in question being

n3+3n2+2n
        6


??????

It can't really be solved at the moment, because you haven't specified what it's equal to. It can be factorised though. If we're doing that, the first thing to notice is that there's a factor of n in there. That can be taken out along with the 6 to give:

n/6 (n²+3n+2).

The term in the brackets is now a quadratic, which factorises fairly easily to give n/6(n+1)(n+2).
If we say that that is equal to 0, then we can solve to give n=0, -1 or -2.


Why did the vector cross the road?
It wanted to be normal.

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