失业率等于失业总人数除以工作年龄人口总数。
参考答案：错
已知圆x2-4x-4+y2=0的圆心是点P，则点P到直线x-y-1=0的距离是（ ）。
He found it difficult ____ others with English. [ ]
A. help
B. to help
C. helped
D. to helping
