复数1+2i3-4i的共轭复数为()A.-15+25iB.-15-25iC.15-25iD.15-25i-数学

题目简介

复数1+2i3-4i的共轭复数为()A.-15+25iB.-15-25iC.15-25iD.15-25i-数学

题目详情

复数
1+2i
3-4i
的共轭复数为(  )
A.-
1
5
+
2
5
i
B.-
1
5
-
2
5
i
C.
1
5
-
2
5
i
D.
1
5
-
2
5
i
题型:单选题难度:中档来源:不详

答案

复数class="stub"1+2i
3-4i
=
(1+2i)(3+4i)
(3-4i)(3+4i)
=class="stub"-5+10i
25
=-class="stub"1
5
+class="stub"2
5
i,∴复数class="stub"1+2i
3-4i
的共轭复数为-class="stub"1
5
-class="stub"2
5
i,
故选 B.

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