function [x,ess,y]=seperate(f,a,b,deta)
fd=diff(f)

if nargin<4
    deta=0.00001
end

if feval(fd,a)*feval(fd,b)>=0
    disp('cannot find superior resolution,please reinput the block')
    return
else
    c=(a+b)/2;
    if feval(fd,c)<0
       a=c;
   elseif feval(fd,c)>0
    
    
    
    

end