9.设α1,α2,···,α8均为n维向量,-|||-(beta )_(1)=(alpha )_(1), (beta )_(2)=(alpha )_(1)+(alpha )_(2) (beta )_(3)=(alpha )_(1)+(alpha )_(2)+(alpha )_(3) ,..., (beta )_(s)=(a)_(1)+(a)_(2)+... +(a)_(s)-|||-证明α1,α2,···,α8线性无关当且仅当β 1,β2,···,β8线性无关