I need some help with an error function

I have a function called 'p' and N is a known parameter that is calculated from a file. The problem is that I didn't found the proper error function for each one of these 3 distributions. Alfa ans beta are the unknown paramers. So the problem is to find the error function for (p(alfa, beta)). If someone could help me I would be very gratefully.

Regards,

Tavi

%1st variant

p= N / ( (alfa*alfa - 2*alfa + 2) * (beta*beta + 2*beta + 2) );

%2nd variant

p= 128*N / (128 + 16 *( ((alfa-beta-2)^ 2)+ ((alfa+beta)^2))+ ((((alfa-beta-2)^ 2) + ((alfa+beta)^ 2))^2));

%3rd variant

%{

abd = (alfa-beta)/2;

p =N/abd * (1-((1 + abd + pow(abd, 2) + pow((alfa + beta), 2)) / 2 + pow((4 * pow(1+abd+pow(abd, 2)/2, 2) + pow (alfa + beta, 2)) , 2)/64));

%}