作业 P34习题2.1 3(2)(3) P39习题2.2 1(2)(3) 2(2)(6)(9)(13).3(1) 预习:P40-49 2021/2/202021/2/20 1 作业 P34习题2.1 3(2)(3). P39习题2.2 1(2)(3). 2(2)(6)(9)(13). 3(1) 预习：P40—49