作者CRAZYAWIND (怒火烧不尽)
看板Grad-ProbAsk
标题Re: [理工] [工数]-ODE~~~~~~~~~~~~~~~~~~~~~~
时间Thu Feb 11 14:38:34 2010
※ 引述《osunriceo (语)》之铭言：
: xy'' + 2y' - xy = 2expx
: ans: y = (A exp(-x) + B expx )/x + expx
: plz hel~
2
因为Q - 1/2P' - 1/4P = -1
令y = uv
∫-1/x dx
u=e = 1/x
x
v" -v = 2e
x -x
vh = c1e + c2e
1 x
vp = ────── 2e
(D+1)(D-1)
x
= xe
x -x x
v = c1e +c2e +xe
x -x x
y = uv = (c1e +c2e )/x +e
--
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1F：推 osunriceo:这招要在甚麽样的情况下用阿,我实在搞不懂用这招的时机 02/11 20:12
2F：→ CRAZYAWIND:都没招可用的情形下用= = 02/11 20:19
3F：推 osunriceo:是喔.......y 02/11 20:37