求行列式1234x123xx12xxx1

ri-r(i+1),i=1,2,...,n-1

0 1 1 ...1 1

0 1-x 1 ...1 1

0 0 1-x ...1 1

......

0 0 0 ...1-x 1

1 x x ...x 1

按第1列展开

D = (-1)^(n+1)*

1 1 ...1 1

1-x 1 ...1 1

0 1-x ...1 1

.....

0 0 ...1-x 1

ri-r(i+1),i=1,2,...,n-2

x 0 ...0 0

1-x x ...0 0

0 1-x ...0 0

......

0 0 ...1-x 1

D = (-1)^(n+1) x^(n-2).