van der Pol equation

tmax = 30;
μ = 1;

sol2 = 
NDSolve[
{x''[t]+μ(((x[t])^2)-1)x'[t] + x[t] == 0,
x[0] == 2,
x'[0] == 0
},
x,
{t,0,tmax}
];

plot2 =
ParametricPlot[
Evaluate[{x[t],x'[t]}/.sol2],{t,0,tmax},
PlotStyle->{Thick,Red},
PlotRange->All
];

sol1 = 
NDSolve[
{x''[t]+μ(((x[t])^2)-1)x'[t] + x[t] == 0,
x[0] == 1,
x'[0] == 0
},
x,
{t,0,tmax}
];

plot1 = 
ParametricPlot[
Evaluate[{x[t],x'[t]}/.sol1],{t,0,tmax},
PlotStyle->{Thick,Blue},
PlotRange->All
];

sol3 = 
NDSolve[
{x''[t]+μ(((x[t])^2)-1)x'[t] + x[t] == 0,
x[0] == 4,
x'[0] == 0
},
x,
{t,0,tmax}
];

plot3 = 
ParametricPlot[
Evaluate[{x[t],x'[t]}/.sol3],{t,0,tmax},
PlotStyle->{Thick,Green},
PlotRange->All
];

Show[
plot1,plot3,plot2,
AxesLabel->{x,(OverDot[x])},
LabelStyle->{Medium,Bold}
]

plot1 =
Plot[
Evaluate[x[t]/.sol1],{t,0,tmax},
PlotStyle->{Thick,Blue},
PlotRange->All
];

plot2 =
Plot[
Evaluate[x[t]/.sol2],{t,0,tmax},
PlotStyle->{Thick,Red},
PlotRange->All
];

plot3 =
Plot[
Evaluate[x[t]/.sol3],{t,0,tmax},
PlotStyle->{Thick,Green},
PlotRange->All
];

Show[
plot1,plot3,plot2,
AxesLabel->{t,x},
LabelStyle->{Medium,Bold}
]

tmax = 30;
μ = 1;

sol2 = 
NDSolve[
{x'[t]== μ(y[t]-x[t](x[t]^2/3 - 1)),
y'[t]== -x[t]/μ,
x[0] == 2,
y[0] == 2/3
},
{x,y},
{t,0,tmax}
];

plot2 =
ParametricPlot[
Evaluate[{x[t],y[t]}/.sol2],{t,0,tmax},
PlotStyle->{Thick,Red},
PlotRange->All
];

sol1 = 
NDSolve[
{x'[t]== μ(y[t]-x[t](x[t]^2/3 - 1)),
y'[t]== -x[t]/μ,
x[0] == 1,
y[0] == -2/3
},
{x,y},
{t,0,tmax}
];

plot1 =
ParametricPlot[
Evaluate[{x[t],y[t]}/.sol1],{t,0,tmax},
PlotStyle->{Thick,Blue},
PlotRange->All
];

sol3 = 
NDSolve[
{x'[t]== μ(y[t]-x[t](x[t]^2/3 - 1)),
y'[t]== -x[t]/μ,
x[0] == 4,
y[0] == 52/3
},
{x,y},
{t,0,tmax}
];

plot3 =
ParametricPlot[
Evaluate[{x[t],y[t]}/.sol3],{t,0,tmax},
PlotStyle->{Thick,Green},
PlotRange->All
];

Fplot =
Plot[
x(x^2/3 - 1),{x,-3,3},
PlotStyle->{Thick,Purple}
];


Show[
Fplot,plot1,plot3,plot2,
AxesLabel->{x,y},
LabelStyle->{Medium,Bold}
]

plot1 =
Plot[
Evaluate[x[t]/.sol1],{t,0,tmax},
PlotStyle->{Thick,Blue},
PlotRange->All
];

plot2 =
Plot[
Evaluate[x[t]/.sol2],{t,0,tmax},
PlotStyle->{Thick,Red},
PlotRange->All
];

plot3 =
Plot[
Evaluate[x[t]/.sol3],{t,0,tmax},
PlotStyle->{Thick,Green},
PlotRange->All
];

Show[
plot1,plot3,plot2,
AxesLabel->{t,x},
LabelStyle->{Medium,Bold}
]