方程（x+2）（x-1）=0的解为______．
∵（x+2）（x-1）=0
∴x+2=0或x-1=0
∴x1=-2，x2=1
故本题的答案是-2或1．
—Philip is the first place winner in the writing competition.
—_________ pleasant surprise this gave his teacher!
A．What
B．What a
C．How
D．How a
润滑油进行三级过滤的目的是。（）
A.滤去油中水份
B.滤去油中机械杂质
C.滤去油中有毒有害物质
D.滤去油中多余添加剂
