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#14e7447f-10b1-452c-8b3f-4378270a308f简单解答题复数的概念与运算复数与推理

27.已知复数z1=a22ai(aR)z_{1}=a^{2}-2ai(a\in R),复数z2z_{2}在复平面内对应的向量为OA=(1,2)\overrightarrow{OA}=(1,-2)
(1)若z1z2z_{1}-z_{2}为纯虚数,求aa的值;
(2)若z1i+z2z_{1}i+z_{2}在复平面内对应的点在第三象限,求aa的取值范围.