A:x2−y2x−y =x﹣y
B:x2−2xy+y2x−y =x﹣y
C:xyx2−xy=yx−y
D:y2−x2xy−yx−xy
machine.
某反应和微观示意图如下,下列说法正确的是()
方程mx2﹣4x+1=0(m<0)的根是( )