已知非零向量 a 、 b 满足 | a + b |=| b | , ①若 a 、 b 共线,则 a =-2 b ; ②若 a 、 b 不共线,则以 | a |、| a +2 b |、2| b | 为边长的三角形为直角三角形; ③ 2| b |>| a +2 b | ; ④ 2| b |<| a +2 b | . 其中正确的命题序号是______.
【简答题】John Steinbeck once said, “All American believe they are born fishermen. For a man to admit to a distaste in fishing would be like speaking publicly against mother-love or hating moonlight”. I can’t s...
【简答题】John Steinbeck once said, “All Americans believe they are born fishermen. For a man to admit to a distaste in fishing would be like denouncing (公开指责) mother – love or hating moonlight.” I can’t say th...