Can anyone tell me what is the command to calculate maximum absolute error in mapple.

  I want to calculate values of constants a[1] and b[1] by NonlinearFit model for two equations mentioned in below

(1/a[1]*x*t)*(1+a[1]*x^(2)*t+2*b[1]*x)    and  (1/b[1]*x*t)*(5*x*t+20*b[1]*a[1]*x*t^2+2*b[1]*x)

I know for the nonlinearfit model we need a data. But in my case, I do not have any data. So maybe data can be obtained by the numerical method, but how I do not know 

Please help me to remove error from the plotting. Here I have attached a mapple file

.u_nonlinerafit.mw