用matlab求这个方程的数值解：y''-(1-y^2)y'+y=0,y(1)=2,y(2)=0,[0,20],麻烦把程

这是你们老师出的题目吧,这个例子在好多书上都出现过。
具体如下：
function dydt = vdp1(t,y)
dydt = [y(2); (1-y(1)^2)*y(2)-y(1)];
end
保存函数文件
[t,y] = ode45(@vdp1,[0 20],[2; 0]);
%This example uses @ to pass vdp1 as a function handle to ode45。The
resulting output is a column vector of time points t and a solution array y。Each row in y corresponds to a time returned in the corresponding row of t。
作图：
You can simply use the plot command to view
the solver output：
plot(t,y(:,1),'-',t,y(:,2),'--')
xlabel('time t');
ylabel('solution y');
legend('y_1','y_2')