Integration in Octave between float point

I am trying to calculate the integral between two float points. The programm can do it, but it sends this next messagge

warning: passing floating-point values to sym is dangerous, see "help sym"

This is my code

i=2.5;syms x yf=((2*x-1)/10)*((2*y-1)/10)/(x+y);variable=double(int(int(f,x,i,1),y,i,1));

is there anyway to do it whithout that inconvenient?