(x1,x2,x3)=(k-1)x1+(k+2)x2+(k+1)x3,若为正定,k的范围?x1 x2 x3都是平方项

(x1,x2,x3)=(k-1)x1+(k+2)x2+(k+1)x3,若为正定,k的范围?x1 x2 x3都是平方项
(x1,x2,x3)=(k-1)x1+(k+2)x2+(k+1)x3,若为正定,k的范围?
x1 x2 x3都是平方项

(x1,x2,x3)=(k-1)x1+(k+2)x2+(k+1)x3,若为正定,k的范围?x1 x2 x3都是平方项
即要求每一项的系数大于零,所以k〉1