, (1)
, .
y 1(x) y 2(x) (1), , . y 1(x) y 2(x) (1) .
:
, , .
D >0, k 1≠ k 2.
D =0, k 1= k 2.
D <0, , .
.
1. k 1≠ k 2 - ; 2. k 1= k 2 - ; 3. - ; 4. - . | 1. ; 2. ; 3. ; 4. . |
()
(2)
f(x) .
, , , , (2).
: = 0 + ỹ 0 - (2) ỹ.
ỹ .
1. ,
n.
ỹ = eαx(Anxn + An-1xn-1 + + A1x + A0)xr,
r , .
A0, A1,, An (), .
, . ỹ (2), , . , ().
2. f(x) = eαx(P(x)cosβx + Q(x)sinβx), P(x), Q(x) . ỹ = eαx(Ak(x)cosβx + Bk(x)sinβx)xr.
k() k() k = (,). r , , β.
k(), k() .
2
|
|
.
) 2 y'' + 5 ' + 2 = 0.
:
2 k 2 + 5 k + 2 = 0,
.
: k1 = -2, k2 = -1/2,
,
- .
) '' + 6 ' + 13 = 0.
:
k 2 + 6 k + 13 = 0,
:
, ,
.
) '' 8 ' + 16 = 0.
:
k 2 8 k + 16 = 0,
.
: k1 = k2 = 4, ,
y = ex(C1 + C2x) - .
) '' 5 ' + 6 = 13sin3 x.
..
' ' 5 ' + 6 = 0.
k 2 5 k + 6 = 0 k1 = 2, k2 = 3.
, 0 = 12 + 23
..
:
13sin3 x = e 0 x (0∙cos3 x + 13sin3 x),
α = 0, β = 3, P0(x) = 0, Q0(x) = 13 . k = α + iβ = 3i k 1 k 2, r = 0
ỹ = e0x(A0(x)cos3x + B0(x)sin3x)x0= Acos3x + sin3x.
:
,
.
,
.
:
-3( + 5 )cos3 x + 3(5 )sin3 x ≡13sin3 x.
sin3 x cos3 x:
, = 5/6, = -1/6.
:
= 5/6 cos3 x 1/6 sin3 x.
:
= 0 + ỹ = 1 2 + 2 3 + 5/6 cos3 x 1/6 sin3 x.