Câu 4:Trang 134-sgk giải tích 12
Tính $\left | z \right |$, với:
a) $z=-2+i\sqrt{3}$
b) $z=\sqrt{2}-3i$
c) $z=-5$
d) $z=-i\sqrt{3}$
Bài Làm:
a) $\left | z \right |=\left | z=-2+i\sqrt{3} \right |$
= $\sqrt{(-2)^{2}+(\sqrt{3})^{2}}=\sqrt{7}$
Vậy $\left | z=-2+i\sqrt{3} \right |=\sqrt{7}$
b) $\left | z \right |=\left | \sqrt{2}-3i \right |$
= $\left | z \right |=\left | \sqrt{2}-3i \right |$
= $\sqrt{(\sqrt{2})^{2}+(-3)^{2}}=\sqrt{11}$
Vậy $\left | \sqrt{2}-3i \right |=\sqrt{11}$
c) $\left | z \right |=\left | -5+0i \right |$
= $\sqrt{(-5)^{2}}=5$
Vậy $\left | -5+0i \right |=5$
d) $\left | z \right |=\left | -i\sqrt{3} \right |$
= $\sqrt{(\sqrt{3})^{2}}=\sqrt{3}$
Vậy $\left | -i\sqrt{3} \right |=\sqrt{3}$