Re: [線代] 問一題線性代數
※ 引述《light0617 (EDWIN)》之銘言：
: 請教板上神人解答
: 1.C=AB,
: A is m*n
: B is n*m m>n
: is C invertible?
: 解答說 rank(C) <=rank(A)<=n ....
: 我想問的是 為什麼rank(C) <=rank(A)???
: rank(C) <=rank(B)嗎??
Another way,
C is invertible iff CX = 0 → X=0
And CX = (AB)X = A(BX) = 0 → X has non-trivial solution, since m > n.
Hence, C is not invertibe.
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