题目7.已知 _(1)=(1,2,3), _(2)=(3,-2,1), _(3)=(2,-3,1), 则-|||-(a)_(1)+3(a)_(2)-5(a)_(3)= ()-|||-A (1,13,4)-|||-B (-1,13,4)-|||-(1,3,4)-|||-D (1,13,14)题目解答答案