, t = 0 x 0 N . , t > 0 x (t). , , .
.
k . t:
.
, :
.
. NC = D, :
x/ (N x) = eNkt + D,
x (t):
.
E = eD. , .
, (0) = 0 0 = N/ a, a > 0, . :
.
2 , a. N 1, k 0,5.
, , , , , , , .
y ¢ + ay = 0. (3)
: . x. , ln y = ax + C, y = eax + C, C ‑ . eC = A, (3) :
y = Aeax. (4)
A, , (3). , (x 1, y 1), (4) A. A (4) (3).
, : (3)
y (0) = y 0. (5)
(3).
(3) (5) ,
y (x) = y 0 eax. (6)
, , , x, . , , (4) ( ), y (x 1) = y 1, .
|
|
(3) a = 0, y (x) = C, , (5) y 0. y (x) y 0 x.
.
y¢ + ay = b, (b = cost) (7)
y (0) = y 0.
(, a ¹ 0). (7) z¢ + az = 0. , z = z 0 eax, . , (7) :
. (8)
(7) a = 0, y (x) = bx + y 0.
, (8) : yh = Aeax ‑ y¢ + ay = 0 y 0(x) = b / a ‑ , , (7) y¢ = 0. (8) (7) ye yh y (x) . x a < 0 a > 0. (a < 0) , ( ).
1 2, yh = (y 0 ye) eax x a > 0 x a < 0.
. . . p , , . , , S (p). , . D (p). E (p) : E (p) = D (p) S (p). E (p) ³ 0, , , , D (p) = S (p) E (p) = 0. E (p) £ 0, , , . , , : , , . .
.
k ‑ , .
: D (p) = a + bp S (p) = g + dp. , p (0) = p 0,
|
|
.
, , ,
,
, b d < 0 b d > 0. b ‑ , d ‑ , b d < 0 ( ), , . b d > 0, : .
2. ()