[理工] 102交大資聯 線代
想討論的如下:
1.If a nonzero matrix is said to be in rref, the properties of this matrix are
(C)<TRUE> if there are rows whose entries are all zero, those rows are below
the rows having nonzero entries.
為什麼是對的呢？我以為全部0是在最後一行，所以選錯
(D)<False> the first nonzero entry in each column is the only nonzero entry
in its row
為什麼是錯的呢？課本有一句是這樣描述rref的：
"每一列最左邊的非零項所在的行的其他元素皆為0"，
感覺跟這句英文很像
3.There are many types of elementary matrices. Which of the following
definitions are elementary matrices?(I:identity matrix)
(D)<False> An nxn matrix is formed from I by reordering its columns.
為什麼是錯的呢，我以為這一句是做行交換，不也是基本矩陣嗎？
另外，這張考卷出現了4次的"shrotest (minimal 2-norm) least-squares solution"
請問這是minimal solution的意思嗎？
感謝~
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