GIA'I PHU.O.NG TRNH
114)
Gia'i phu.o.ng trnh:
y”−3y0
+ 2y= 2x2
−5 + 2ex
cosx2HD gia’i: λ2
−3λ+ 2 = 0 ⇔λ1
= 1; λ2
= 2NTQ:
y =C1
ex
+C2
e2x
Tm nghi^e.m ri^eng da.ng:
y=α1
(x)ex
+α2
(x)e2x
bang cach bi^en thi^en hang s^o:
(α0
1
ex
+α2
0
e2x
= 0α0
1
ex
+α2
0
(2e2x
) = 2x2
−5 + 2ex
cosx 2α0
1
=−e−x
(2x2
−5)−2 cosxα0
2
=e−2x
(2x2
−5) + 2e−x
cosxα1
=e−x
(2x2
−4x−1)−4 sinx⇒α2
=−12[e−2x
(2x2
−5) + 2(xe−2x
+ 12e−2x
)] + 83(−e−2x
cosx2 + 12e−x
sinx