# Math Help - Roots of equation

1. ## Roots of equation

Hi, can anyone help me to prove this:

If the roots of the equation

$x^3-Lx^2+mx+n=0$

are the cosine of the angles of a triangle

show that: $L^2=2m+2n+1$

2. ## Re: Roots of equation

Well, you have three angles. Use them and see what happens.

$\alpha$, $\beta$, $\pi - \alpha-\beta$

You have a Law of Cosines.

Show us what you get.