A:,
B:2R,
C:R, R
D:R,
7的6倍是____,30是5的____倍。
________that she is interested in children,I am sure teaching is the right job for her.
在平面直角坐标系xOy中,设直线y=﹣x+2与圆x2+y2=r2交于A,B两点,O为坐标原点,若圆上一点C满足OC→=54OA→+34OB→则r=____