分解反应:____
化合反应:____
置换反应:____.
已知点A(x1,y1)、B(x2,y2)在反比例函数y=7x的图象上,且x1<0<x2,则y1、y2和0的大小关系( )
等差数列an前n项和为Sn,满足S20=S40,则下列结论中正确的是( )
Jane a story book when her mother came into her bedroom.