y※ 引述《h888512 (理論型嘴砲)》之銘言：
: (4)
: d y
: ------ + ky =0
: (4)
: d x
: k is a positive constant
: 很弱的問題...
: 謝謝!!
4
( D + k ) y = 0
4 2 2
( D + 2D √k + k - 2D √k )y = 0
2 2 1/4 2
( ( D + √k ) - (√2D k ) ) y = 0
2 1/4 2 1/4
( D + √k + √2D k )(D + √k - √2D k ) y = 0
1/4
-√2 k ±√(2√k - 4√k)
D = ───────────────
2
1/4
√2 k ±√(2√k - 4√k)
D = ───────────────
2
1/4 1/4 1/4
- k /√2 x k k
y = e ( c1 cos(─── x) + c2 sin(───) ) +
√2 √2
1/4 1/4 1/4
k /√2 x k k
e ( c3 cos(─── x) + c4 sin(───) )
√2 √2
Gerenral solution
--
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 114.42.86.138
更正哩^^
※ 編輯: ntust661 來自: 114.42.86.138 (10/05 00:11)