Viète's Formulas/Examples/Cubic

Example of Use of Viète's Formulas
Consider the cubic equation:
 * $x^3 + a_1 x^2 + a_2 x^1 + a_3 = 0$

Let its roots be denoted $x_1$, $x_2$ and $x_3$.

Then:

Proof
A specific instance of Viète's Formulas for $n = 3$.