curve fitting coefficients.

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get the model coefficients, but I can not use them to plot the graph. How to solve?

see the code:

dados = [(0, -0.183440428023042),
 (0.200000000000000, -0.131101157495126),
 (0.400000000000000, 0.0268875670852843),
 (0.800000000000000, 0.110532679260319),
 (1.00000000000000, 0.253944632998395),
 (1.20000000000000, 0.257190123748649),
 (1.40000000000000, 0.531888837111346),
 (1.60000000000000, 0.579048247883555),
 (2.00000000000000, 0.935180993484717),
 (2.20000000000000, 0.916600344376623),
 (2.60000000000000, 1.13328608090532),
 (2.80000000000000, 1.26893326843583),
 (3.00000000000000, 1.10202945535186),
 (3.40000000000000, 1.13391615491257)]

point(dados,color = "red",size=20,legend_label="pontos coletados")

modelo(x) = a*x+b;modelo

a,b = find_fit(dados, modelo);a;b

modelo(x) = a*x+b

point(dados,color = "red",size=20,legend_label="pontos coletados") + plot(modelo(x),(x,0,3))
Traceback (click to the left of this block for traceback)
...
ValueError: Variable 'x' not found