设a,b,c∈R则复数(a+bi)(c+di)为实数的充要条件是（）_刷题宝

题干

设a,b,c∈R则复数(a+bi)(c+di)为实数的充要条件是（）

A：ad-bc=0

B：ac-bd=0

C：ac+bd=0

D：ad+bc=0

上一题下一题 0.0难度选择题更新时间:2020-02-13 05:09:23

答案(点此获取答案解析）

D

同类题1

观察下列各式：

\sqrt{2 - \frac{2}{5}} = 2 \sqrt{\frac{2}{5}}

\sqrt{3 - \frac{3}{10}} = 3 \sqrt{\frac{3}{10}}

\sqrt{4 - \frac{4}{17}} = 4 \sqrt{\frac{4}{17}}

\sqrt{9 - \frac{m}{n}} = 9 \sqrt{\frac{m}{n}}

，则n﹣m=（）

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B: Mr. Zhao. Look! He is playing basketball there.

A: Nice talking to you. Thank you.

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下列国家中，不是地跨两大洲的国家是

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《旧唐书》称：武则天“制公卿之死命，擅王者之威力”（意为诛杀公卿，独断专权）。武则天遗言无字碑，由后人评价自己的功过。史学家之所以肯定武则天主要是因为（）

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π

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