matlab中各语句之间必须用分号?空格不行?

是的,可以加分号的,
也可以不加,但是要换行才行
比如
>> a=rand(5)*10
a =
8.2141 7.3821 4.1027 0.0986 2.7219
4.4470 1.7627 8.9365 1.3889 1.9881
6.1543 4.0571 0.5789 2.0277 0.1527
7.9194 9.3547 3.5287 1.9872 7.4679
9.2181 9.1690 8.1317 6.0379 4.4510
>> a(4:5,:)=[]
a =
8.2141 7.3821 4.1027 0.0986 2.7219
4.4470 1.7627 8.9365 1.3889 1.9881
6.1543 4.0571 0.5789 2.0277 0.1527