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由点P(2,4)向直线ax+y+b=0引垂线,垂足为Q(4,3),则z=a+bi...
由点P(2,4)向直线ax+y+b=0引垂线,垂足为Q(4,3),则z=a+bi的模为( )
A.
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B.
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C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131023212147954832982/SYS201310232121479548329001_ST/2.png)
D.
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