In order eq. ( 1) shows a positive maximum in the interval ∈ 0,1 , the following restrictions on parameters must old:and this second condition is always satisfied for 0.In order eq. ( 2) shows a positive maximum in the interval ∈ 0,1 , the following restrictions on parameters must hold:and Passing to study the function described by eq. ( 3), it has two points of maximum: and ≡ , .In order the function described by eq. ( 3) may be approximated by a 2nd-order function in the interval ∈ 0,1 , the following restrictions on parameters must hold: