Re: [理工] [線代] 100交大資工

看板Grad-ProbAsk作者goldflower (金色小黃花)時間10年前 (2016/01/22 01:07)推噓2(2推 0噓 7→)

留言9則, 5人參與討論串2/2 (看更多)

各位正取生好我對這題有點疑惑剛好以前有人問過挖出來一下@@ 題目如下: ※ 引述《manual (QQ...)》之銘言： 1 2 1 2 8. Consider a matrix A = [ 1 2 2 5 ] and a system of linear equations 0 0 1 3 -1 Ax = b = [ 3 ] . Which of the following vectors c will make the two systems 1 Ax = b + c and Ax = b have the same least-square error. T A. c = [0, -1, -1] T B. c = [3, 2, 2] T C. c = [1, 0, -1] T D. c = [2, 1, 2] T E. c = [1, 2, 1] Ans: ACE 我自己的想法是把下面兩式聯立 T T A Ax = A b .... (1) Ax = b + c .... (2) T T T 把(2)帶入(1) => A (Ax) = A (b + c) = A b T => A c = 0 T => c = N(A ) 以上為原文內容我一開始的做法跟以上類似推出c屬於ker(trans(A))=perp(R(A)) 但是我得不出答案所以我改用圖解一用圖解很明顯可以看出c屬於R(A) 而且答案就如同解答了了我想問的是請問以上的推論哪裡有問題呢@@ 原文章沒有關於此推論正確與否的解答(當然應該是錯誤的) 感謝回答QQ -- ※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 61.60.217.209 ※ 文章網址: https://www.ptt.cc/bbs/Grad-ProbAsk/M.1453396030.A.FCA.html

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qu3899

01/22 03:01, , 1^F

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qu3899

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jerry031181

01/22 10:45, , 3^F

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