Question: Error: Newton iteration is not converging..

restart; b := 20; de1 := diff(f(eta), eta, eta, eta)+f(eta)*(diff(f(eta), eta, eta))+1-(diff(f(eta), eta))^2+k*(f(eta)^2*(diff(f(eta), eta))-2*f(eta)*(diff(f(eta), eta))*(diff(f(eta), eta, eta))) = 0, diff(theta(eta), eta, eta)+Pr*f(eta)*(diff(theta(eta), eta)) = 0, f(0) = 0, (D(f))(0) = 1, theta(0) = 1, (D(f))(b) = 0, theta(b) = 0; d1 := subs(Pr = .5, k = 1, [de1]); d2 := subs(Pr = 1, k = 1, [de1]); d3 := subs(Pr = 1.5, k = 1, [de1]); d4 := subs(Pr = 2, k = 1, [de1]); da1 := dsolve(d1, numeric); da2 := dsolve(d2, numeric); da3 := dsolve(d3, numeric); da4 := dsolve(d4, numeric); da1(0); da2(0); da3(0); da4(0); with(plots); p1 := odeplot(da1, [eta, diff(f(eta), eta)], linestyle = 1, color = black, legend = "Le = 0.8"); p2 := odeplot(da2, [eta, diff(f(eta), eta)], linestyle = 2, color = black, legend = "Le = 1.0"); p3 := odeplot(da3, [eta, diff(f(eta), eta)], linestyle = 3, color = black, legend = "Le = 1.5"); p4 := odeplot(da4, [eta, diff(f(eta), eta)], linestyle = 4, color = black, legend = "Le = 2.0"); plots[display]({p1, p2, p3, p4}); p5 := odeplot(da1, [eta, theta(eta)], linestyle = 1, color = black, legend = "Le = 0.8"); p6 := odeplot(da2, [eta, theta(eta)], linestyle = 2, color = black, legend = "Le = 1.0"); p7 := odeplot(da3, [eta, theta(eta)], linestyle = 3, color = black, legend = "Le = 1.5"); p8 := odeplot(da4, [eta, theta(eta)], linestyle = 4, color = black, legend = "Le = 2.0"); plots[display]({p5, p6, p7, p8});