分解因式:3x3-12xy2.
原式=3x(x2-4y2)
=3x(x-2y)(x+2y).
While teaching advanced auditing classes, Jones has published his work in ______.
真空中有两个点电荷,它们间的静电力为F,如果保持它们所带的电量不变,将它们之间的距离增大为原来的3倍,它们之间静电力的大小等于[ ]
A.3F
B.F/3
C.F
D.F/9