馥荔子
幼苗
共回答了26个问题采纳率:80.8% 举报
z的共轭复数为4-3i或-4+3i
方法一 (3+4i)(a+bi)=(3a-4b)+(4a+3b)i是纯虚数,
∴
![](https://img.yulucn.com/upload/1/41/141460de9d56be740935a45eb61d60e0_thumb.jpg)
,∴b=
![](https://img.yulucn.com/upload/e/63/e63134bba8b765055fc86c6d7bb0ae40_thumb.jpg)
a,代入a
2 +b
2 =25,得a=±4.
∴a=4时,b=3;a=-4时,b=-3.
∴z=4+3i或z=-4-3i.
故所求的z的共轭复数为4-3i或-4+3i.
方法二 设(3+4i)(a+bi)=ki(k∈R,k≠0),
∴a+bi=
![](https://img.yulucn.com/upload/9/07/90795eb3fc31deb1593453210d549ea1_thumb.jpg)
=
![](https://img.yulucn.com/upload/c/2e/c2e2e52a72f62b21ba85cc819522ffa1_thumb.jpg)
=
![](https://img.yulucn.com/upload/0/e0/0e09a4c74bc503f26c3f9d37c105c274_thumb.jpg)
,
∴a=
![](https://img.yulucn.com/upload/7/f7/7f7913806b224a2a7418107c3e4fa6d7_thumb.jpg)
,b=
![](https://img.yulucn.com/upload/5/dd/5dddce426d10ed2fa755498bcc8188ad_thumb.jpg)
,代入a
2 +b
2 =25,得k=±25.
∴k=25时,z=4+3i,
![](https://img.yulucn.com/upload/9/59/959b0869cd123e32893c4ad5f6d3e385_thumb.jpg)
=4-3i;
k=-25时,z="-4-3i,"
![](https://img.yulucn.com/upload/9/59/959b0869cd123e32893c4ad5f6d3e385_thumb.jpg)
=-4+3i.
1年前
9