题目

如果z=a2+a-2+(a2-3a+2) i为纯虚数,则实数a的值为______________. 答案：解析:z为纯虚数,则由①得a=-1或a=2;由②得a≠1且a≠2,∴a=-1.答案:-1 ．—Who did you stay with ?     —___________.        A．Mr Green’s     B．The Greens      C．Greens     D．The Mr Green’s