matlab矩阵变换利用matlab矩阵访问命令对下面的矩阵做初等行变换使其成为一个上三角矩阵A=1 -2 -1 0 2-2 4 2 6 -62 -1 0 2 33 3 3 3 4

Question

matlab矩阵变换
利用matlab矩阵访问命令对下面的矩阵做初等行变换使其成为一个上三角矩阵
A=1 -2 -1 0 2
-2 4 2 6 -6
2 -1 0 2 3
3 3 3 3 4

Answer 1

A=[1 -2 -1 0 2
-2 4 2 6 -6
2 -1 0 2 3
3 3 3 3 4 ];
for i=2:4
A(i,:)=A(i,:)-A(i,1)/A(1,1)*A(1,:);
end
k=find(A(2:4,2));
k=k(1)+1;
t=A(2,:);
A(2,:)=A(k,:);
A(k,:)=t;
for i=3:4
A(i,:)=A(i,:)-A(i,2)/A(2,2)*A(2,:);
end
k=find(A(3:4,3));
c=size(k);
if (c(1)~=0)
k=k(1)+2;
t=A(3,:);
A(3,:)=A(k,:);
A(k,:)=t;
A(4,:)=A(4,:)-A(4,3)/A(3,3)*A(3,:);
else
k=find(A(3:4,4));
k=k(1)+2;
t=A(3,:);
A(3,:)=A(k,:);
A(k,:)=t;
A(4,:)=A(4,:)-A(4,4)/A(3,4)*A(3,:);
end