.3y + y‘= sin(x)这道题的微分方程怎么接啊,

.3y + y‘= sin(x)这道题的微分方程怎么接啊,
.3y + y‘= sin(x)这道题的微分方程怎么接啊,

.3y + y‘= sin(x)这道题的微分方程怎么接啊,
设y=asinx+bcosx代入得
(3a-b)sinx+(3b+a)cosx=sinx
3a-b=1
3b+a=0
解得a=3/4,b=-1/4
所以y=(3sinx-cosx)/4

y=a(sin(x-b))
代入得a, b