Writing this constraint in gurobi?

Question

I am trying to create this constraint:

using this code:

 for i in range(len(b)):
        for j in range(n):
            gm.addConstr(r <= (b[i] - a[j,i]*x)/ (np.linalg.norm(a[j])))

but keep getting answers that do not make sense. Is there something I am missing?