x3+2xy-x-xy2.
原式=x(x2+2y-1-y2)
=x[x2-(y2-2y+1)]
=x(x+y-1)(x-y+1).
—I called you yesterday afternoon, but there was no reply.
—I ______ a dolphin show in the zoo with my cousins. [ ]
A. watched
B. will watch
C. am watching
D. was watching
如图所示,理想变压器的原、副线圈匝数比为1:5,原线圈两端的交变电压为,氖泡在两端电压达到100V时开始发光,下列说法中正确的有
A.开关接通后,氖泡的发光频率为100Hz
B.开关接通后,电压表的示数为100V
C.开关断开后,电压表的示数变大
D.开关断开后,变压器的输出功率不变