There are a lot of ________ friends.
A:way to make
B:ways of make
C:ways to make
D:way making
C一定时,D和E成____比例.
D一定时,C和E成____比例.
E一定时,C和D成____比例.
设P={x|x2﹣2x﹣3≤0},a= 2 ,则下列关系中正确的是( )
因式分解:xy﹣7y=____.