- 859 名前：１３２人目の素数さん mailto:sage [2016/03/27(日) 01:03:58.55 ID:aFnU9GTM.net]
- >>801
2-(1)
By the formula for Vandermonde determinant
det A=(b+2)(b-a)(a+2).
Notice that det(A)=0⇔rank(A)<3 and the given conditions a<0 and b>0,
rank(A)=2⇔(a=b ∧ a≠-2) ∨ (a≠b ∧ a=-2)
(for rank(A)=1⇔a=b ∧ a=-2)
