A:(a﹣3)2=a2﹣9
B:a2•a4=a8
C:9 =±3
D:−83 =﹣2
如图所示的电路中,电源电压保持不变.闭合开关S,当滑动变阻器的滑片P向左移动时,电流表A1和A2示数的变化情况分别是( )
The book is ________. I wrote ________ name on its cover for ________.
实验室为测定某硫酸铜溶液的浓度,现提供氢氧化钠固体进行实验.