m^#a^^^ikmaf-ab^^ 课堂程序提供给大家参考:clear %%%%%% 求方程 1 2 syms lamda t x mu y x=dsolve('Dx=-lamda*x','x(0)=1100','t') y=dsolve('Dy=lamda*1100*exp(-lamda*t)-mu*y','y(0)=0','t') >> x=dsolve('Dx=-lamda*x','x(0)=1100','t') x = 1100/exp(lamda*t) >> y=dsolve('Dy=lamda*1100*exp(-lamda*t)-mu*y','y(0)=0','t') y = (1100*lamda)/(exp(mu*t)*(lamda - mu)) - (1100*lamda)/(exp(lamda*t)*(lamda - mu)) %作图 1 t=0:0
1:25; y=6600*(exp(-0
1155*t)-exp(-0
1386*t)); x=1100*exp(-0
1386*t); plot(t,x,t,y) grid on % 计算药量达到400mg 的时间 t1,即求出 t1=4
87 tt=fzero('6600*(exp(-0
1155*x)-exp(-0
1386*x))-400',[0,8]) >> tt=fzero('6600*(exp(-0
1155*x)-exp(-0
1386*x))-400',[0,8]) tt = 4
8659 %%%%%%% 以下程序是求出P12 中 t2=7
89 syms xx y=6600*(exp(-0
1155*xx)-exp(-0
1386*xx))-400; z=diff(y,xx) z = 22869/(25*exp((693*xx)/5000)) - 7623心 0*exp((231*xx