A:原子的核电荷数是31
B:元素符号是Ga
C:属于金属元素
D:相对原子质量为69.72g
— Could you tell me _____? I must find him.
— Sorry, I have no idea. But he was here just now.
羊年的新春灯会上,人们将街道两旁挂满了灯笼,并在街道一侧从1开始按顺序编号,直到街尾,然后从对面的灯笼开始往回编号,到编号为1的灯笼对面结束.每个灯笼与对面灯笼恰好相对.若编号36的灯笼与编号65的灯笼相对,那么所有灯笼的号码和为多少?
化简:(a﹣1)(a+1)﹣(a﹣1)2.