Question
If ${z^2} + z + 1 = 0$, $z \in C$, then
$\left| {\sum\limits_{n = 1}^{15} {{{\left( {{z^n} + {{( - 1)}^n}{1 \over {{z^n}}}} \right)}^2}} } \right|$ is equal to _________.
Correct Answer
2
If ${z^2} + z + 1 = 0$, $z \in C$, then
$\left| {\sum\limits_{n = 1}^{15} {{{\left( {{z^n} + {{( - 1)}^n}{1 \over {{z^n}}}} \right)}^2}} } \right|$ is equal to _________.