the last commit for lab6 exercises and a2 exercises

lab1/lab1.m

@@ -0,0 +1,13 @@
+a=[2,3,6,7;4,2,8,6;3,6,9,2;4,7,9,3]
+a1=a([1:3],[2:3])
+a2=a(2,3)
+zeros(3,4)
+ones(5)
+eye(3)
+rand(4)
+randn(3)
+% 删除行列
+a(:,[3])=[]
+% 增加元素和列
+a(5,6)=45
+a(:,4)=[90,89,34,56,98]