若一个正数的平方根是-a+1和2a,则这个正数是______.
根据题意得:-a+1+2a=0,解得:a=-1,
则这个正数是:(-2)2=4.
故答案是:4.
如果一国本位制度中规定货币单位受等量金属或他国货币等价的约束,成为( )。
A.(A) 准本位制
B.(B) 复本位制
C.(C) 绝对本位制
D.(D) 规范本位制
She has been skating for _____. [ ]
A. three and half years
B. three and half a year
C. three and a half year
D. three years and half