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ForeverAutumn* Offline
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Rational Root Theorem? - February 10th 2009, 12:57 AM

My math book doesn't explain it at all and I don't have any notes from class - can anyone help me with the rational root theorem?

The equation I'm stuck on:

x(to the fourth power) + 4x(cubed) - 3x(squared) - 14x - 8

I did the P/Q thing and used synthetic division, that brought me to
(x-2) (x[cubed] + 6x[squared] + 9x + 4

I've absolutely no idea where to go from here. Help? I know I need to factor down the equation so I can fit it into the quadratic formula, then find the roots from there but I've no idea how to get past the x cubed.

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Re: Rational Root Theorem? - February 10th 2009, 02:43 AM

Well I guessed substitutes and found than -1 makes
x - 6x +9x + 4 equal 0 so this makes (x+1) a factor of x - 6x +9x + 4 so dividing through by (x+1) gives x + 7x + 4 = 0 which in turn has roots of [-7+sqrt(33)]/2 or [-7-sqrt(33)]/2
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