Viète's Formulas/Examples/Cubic with Equal Roots

Example of Use of Viète's Formulas
The coefficient of $x$ in the expansion of cubic $\paren {x - 1}^3$ is $3$.

Proof
The expansion:


 * $\paren {x - 1}^3 = x^3 + a_2 x^2 + a_1 x + a_0$

Viète's Formulas for $z_1 = z_2 = z_3 = 1$ are: