【单选题】如果关于x的方程x 2 -2x-a=0的一个根是i,那么复数a [ ]
【判断题】绝对黑体是指在任何的的温度下,对任何波长的辐射都能全部吸收的物体。
【单选题】When utilizing the percentage of sales approach, managers: I. estimatecompany sales based on a desired level of net income and the current profitmargin. II. consider only those assets that vary direct...
【简答题】如果复数 是纯虚数,那么实数 等于_________
【单选题】在任何温度下,绝对黑体对任何波长的辐射能的吸收比( )。
【单选题】如果实数b与纯虚数z满足关系式(2-i)z=4-bi(其中i是虚数单位),那么b等于( )
【单选题】下面命题: ①0比-i大; ②两个复数互为共轭复数,当且仅当和为实数时成立; ③x+yi=1+i的充要条件为x=y=1; ④如果让实数a与ai对应,那么实数集与纯虚数集一一对应. 其中正确命题的个数是( )
【单选题】—We all agree________Tom.. Has the project been passed? — Who________Tom can make the final decision?
【简答题】A: Hey, David. Long time no see. What are you now? B: I’m a sales manager for Asia in a company. __1__ A: Wow!__ 2_ B: It can be, but_ 3_. And my own manager can give me support if there is any big pr...