gaokao 2019 Q1

gaokao · China · beijing-science 5 marks Complex Numbers Arithmetic Modulus Computation

Given the complex number $z = 2 + \mathrm { i }$, then $z \cdot \bar { z } =$ (A) $\sqrt { 3 }$ (B) $\sqrt { 5 }$ (C) 3 (D) 5

Given sets $M = \{ x \mid - 4 < x < 2 \} , N = \left\{ x \mid x ^ { 2 } - x - 6 < 0 \right\}$

Given the complex number $z = 2 + \mathrm { i }$, then $z \cdot \bar { z } =$
(A) $\sqrt { 3 }$
(B) $\sqrt { 5 }$
(C) 3
(D) 5