= +
+ −
= ⋅ +
=
= ⎡ ⎣⎢
⎤ ⎦⎥
×
→ +
→ → +β β
− ⎛ ⎝⎜
⎞ ⎠⎟
= λ
dN dt
2⎡ ⎣⎢
− λ -λ -λ
− λ − λ -λ
[ ] [ ]
λ λ
-