“挖”、“补”也须谨慎

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相传女祸补天时费了九牛二虎之力,在数学世界里,同样需要我们采取“挖”、“补”的方法,并须慎之又慎,稍一疏忽,就会产生错解.下面举例说明. 例题已知复数w=(3-z)/(3+z)(z≠±3)是纯虚数,求复数μ=6i-z的辐角主值范围. 解W是纯虚数 ,故复数z对应的轨迹是以(0,0)为圆心3为半径的圆,并除去(±3,0)两点. According to legend, women’s misfortunes took up a tortoise of talents. In the mathematics world, we also need to adopt “digging” and “complement” methods, and we must be cautious. If we neglect one point, we will have misunderstandings. Below For example, an example of a complex number w=(3-z)/(3+z)(z≠±3) is a pure imaginary number. Find the main value range of the complex angle μ=6i-z. The solution W is purely imaginary. Therefore, the locus corresponding to complex z is a circle with radius (0,0) as its center 3, and removes (±3,0) points.
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