I know this is really stupid and I should get this but
P(x)=x³+3x+2 with roots alpha, beta, gamma
find eqt. with roots alpha + 1/alpha etc. (a+1/a)
x=a+1/a,
a=(x+(x²-4)^½)/2 - right? =/
anyways, I tried subbing that in and expanding but it ain't working. should I just try and find...