(1)把(x-y)当作一个因式,对3(x-y)²-7(x-y)+8(x-y)²+5(x-y)合并同类
(1)把(x-y)当作一个因式,对3(x-y)²-7(x-y)+8(x-y)²+5(x-y)合并同类项后得-------------------------
(2)如果长方形的一边长为2m+n,比另一边多m-n(其中m>n),则长方形的周长是--------------------------------
(3)6a²-2ab-2(3a²+½ab)的结果是( )
A.-3ab B.-ab C.3a² D.9a²