Those are _____________.[ ]
A. their cloth
B. their clothes
C. his ruler
D. her ruler
答案:B
因式分解:
(1)﹣4a3b2+10a2b﹣2ab;
(2)6(x+y)2﹣2(x+y);
(3)﹣7ax2+14axy﹣7ay2;
(4)25(a﹣b)2﹣16(a+b)2;
(5)(x2+y2)2﹣4x2y2;
(6)a2+2ab+b2﹣1.
按照熔焊接头坡口形状不同分类,属于基本形坡口的有( )。
A.J形坡口
B.单边V形坡口
C.Y形坡口
D.卷边坡口