GIA'I PHU.O.NG TRNH
118)
Gia'i phu.o.ng trnh:
y” + 2y0
+y= sinx+ e−x
xHD gia’i:Phu.o.ng trnh da.c tru.ng
λ2
+ 2λ+ 1 = 0⇔λ=−1(b^o.i 2)
Nghi^e.m t^o'ng quat:
y=e−x
(C1
x+C2
).Tm nghi^e.m ri^eng da.ng:
y=α1
(x)xe−x
+α2
(x)xe−x
Bi^en thi^en hang s^o:
α1
= ex
α0
1
=ex
sinx+ 12(sinx−cosx) + ln|x|⇒α0
2
=−xex
sinx− xα2
=−[xex
22 (sinx−cosx) + ex
2 cosx]− x2
4Suy ra nghi^e.m t^o'ng quat:
y=e−x
(C1
x+C2
) +xe−x
ln|x| − cos2x − x2
e4−x