Casio function calculators, fx-82ES and fx-99 1CN, fx-82ES are cheaper and use batteries; Fx-99 1CN has more and more functions than fx-82ES. Fx-99 1CN{ calculation, complex number, radix, matrix, statistics, vector, inequality, table, equation, function, proportion} Solve equations and see what kind of function you need. I have been using Casio Fx-99 1CN function calculator for more than a year, just like a new one.