[理工] 工數+線代
★Solve the diggerential eqaution
2
(2y +3x)dx + (2xy)dy = 0
c
→y = ±√ (─ - x ) _______(1)
x^2
2 c
→y = -x + ─ _________(2)
x^2
(A) if y(1)=2 then y(-1) = √6
(B) if y(1)=-2 then y(-1) = √6
(C) if y(1)=2 then y(-1) = -√6
(D) if y(1)=-2 then y(-1) = -√6
若用(1)當依據找答案 得 AD
若用(2)當依據找答案 得ABCD 覺得應該是(1) 但說不出(2)錯在哪
請打大家幫我勘誤一下 感恩 ..
★ n
For any n*n matrix H , if there is an orthogonal basis for R
consisting of eigenvectors of A
這段話的意思 A 和 H 直覺上的關聯應該是 ...?
把orthogonal basis塞進H 當col 變成 orthogonal matrix
T
或是 H的特徵值可以對應到A 所以得 H = H ?
T
另外 orthogonal matrix 滿足 HH = I 為何不叫 orthogormal matrix呢
(純好奇而已 ....)
★ For any vector space W
n
→If W is finite-dimensional ,then W is a subspace of R
for some positive integer n
True or False ? 答案給F
n
但...錯在哪呢 ? W為R 中n維子空間 其中n為正
還是n可以為0 就得到反例 n不一定要正整數 ? 或是我理解錯誤 ....
★Let v be a finite - dimensional vector space, and let
U1 U2 U3 be its subspaces
→dim(U1+U2+U3) = dimU1 + dimU2 + dimU3 - dim(U1∩U2)
- dim(U2∩U3) - dim(U1∩U3) + dim(U1∩U2∩U3)
乍看之下我會覺得是對的
T T
But if U1=span[1 0 0] U2 = span[0 1 0]
T T
U3=span{[1 1 0] [0 0 1] } 會變成 3 = 4矛盾
還是那式子根本不存在呢 @@? 感覺這是微度定理的延伸 !
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◆ From: 125.224.72.36
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※ 編輯: mp8113f 來自: 125.224.72.36 (02/01 00:22)
還有 68 則推文
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