- $\left| z \right|\sqrt 2 \ge \left| a \right| + \left| b \right|$
- $\left| z \right| \ge \sqrt 2 a + b$
- $\left| z \right|\sqrt 2 \le \left| a \right| + \left| b \right|$
- $\left| z \right| \ge \sqrt 2 \left| a \right| + \left| b \right|$