12x2-2y2=12(x2-4y2)=12(x+2y)(x-2y).
故答案为:12(x+2y)(x-2y).
He’s never read this book before, ________?
A. isn’t he B. does he C. has he
细胞中含量最多的元素和组成生物体的最基本的元素分别是()
A.C,O
B.H,C
C.O,C
D.O,N