用matlab画微分方程的相图

dx./dt=y*(4+x^2-y^2)

dy./dt=-x(-2-x^2+y^2)
请写出这方程的matlab相图做法的源程序！

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clear;clc

[x,y]=meshgrid(linspace(-5,5));

streamslice(x,y,y.*(4+x.^2-y.^2),-x.*(-2-x.^2+y.^2));

xlabel('x'指掘);ylabel('镇逗消y'御知);

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