Skip to content / Đến nội dung
ThichHocToan.com

2019 AMC 12A Question 21

AMC12 · 2019 AMC 12A

Question 21

Let $$
z = \dfrac{1 + i}{\sqrt{2}}.
$$ What is

$$
\begin{aligned} &\left(z^{1^2} + z^{2^2} + z^{3^2} + \cdots + z^{12^2}\right) \\ &\quad {}\cdot \scriptsize \left(\dfrac{1}{z^{1^2}} + \dfrac{1}{z^{2^2}} + \dfrac{1}{z^{3^2}} + \cdots + \dfrac{1}{z^{12^2}}\right)? \end{aligned}
$$
  1. $18$
  2. $72 - 36\sqrt{2}$
  3. $36$
  4. $72$
  5. $72 + 36\sqrt{2}$