设复数zz∈C在映射f下的象是Z-·i,则-1+2i的原象为( )
The story of Lei Haiwei, the winner of The Poetry Conference(诗词大会), again proved that it's necessary not to ____.
某学习小组进行测定花生长度大小实验,取样时提出下列四种方法,正确的是( )