1. A control method for a modeling system that designs by computer processing, the method comprising: a. obtaining a math equation from a model to be designed; b. finding a first solution from said math equation; c. finding a second solution from said math equation with one coefficient expanded in series set as an interval; d. finding a first distance between a first vector and a second vector with a coefficient of said first solution set as said first vector and with a coefficient of said second solution set as said second vector; e. finding a third solution from said math equation with said one coefficient set to zero in response to the fact that said first distance is not greater than a predetermined value, wherein if said first distance is greater than the predetermined distance, above steps c-e are iteratively repeated until said first distance is not greater than the predetermined value; f. finding a second distance between said first vector and a third vector with a coefficient of said third solution set as said third vector; and g. determining that a term of said one coefficient in the math equation is omissible, in response to the fact that said second distance is not greater than a predetermined value, wherein each of said first and second distances is a Mahalanobis distance.