把t和k省略i' = -λiss' = λis - αs(s+r)r' = αs(s+r)则i'+s'+r' = 0积分得i + s + r = C得到s = i'/(-λi)s' = [i'/(-λi)]'s + r = C - i代入第二个方程,得到[i'/(-λi)]' = -i' - αi'/(-λi) * (C-i)整理得i'...