TM NGHI^E.M T^O'NG QUAT CU'A PHU.O.NG TRNH
130)
Tm nghi^e.m t^o'ng quat cu'a phu.o.ng trnh:
y00
+y= sinx+ cos 2x.HD gia’i:Phu.o.ng trnh da.c tru.ng
λ2
+ 1 = 0 ⇐⇒ λ1
=±i. Nghi^e.m t^o'ng quat cu'a
phu.o.ng trnh tuy^en tnh thu^an nh^at tu.o.ng u.ng:
y = C1
cosx+C2
sinx. Tm nghi^e.m
ri^eng da.ng:
y∗
=y1
+y2
; vo.i
y1
la nghi^e.m ri^eng cu'a
y00
+y= sinx, du.o..c
y1
=−12xcosxva
y2
la nghi^e.m ri^eng cu'a
y00
+y= cos 2x, du.o..c
y2
=−13cos 2x. V^a.y nghi^e.m t^o'ng quat:
y =C1
cosx+C2
sinx− 12xcosx− 13cos 2x