(3a-y)(3a+y)是下列哪一个多项式因式分解的结果[ ]
A.9a2+y2
B.-9a2+y2
C.9a2-y2
D.-9a2-y2
答案:C
铸造金属全冠预备体牙合面至少磨除()
A.0.3mm
B.0.5mm
C.0.9mm
D.1.2mm
E.2.0mm
吻合效应