①作出△ABC关于原点O中心对称的图形;
②将△ABC绕原点O按顺时针方向旋转90°后得到△A1B1C1,画出△A1B1C1,并写出点A1的坐标.
A1(﹣1,1).
①Al,Fe ②Cl2,S ③Mg,C ④H2,Cu ⑤C,Si.
— Sorry for being late again.
— here on time next time, or you'll be punished.