/diy/ - Do It Yourself

ok what the fuck is this circuit, i've tried it with all sorts of different frequency and amplitude sine waves, with different waves at each input
i thought i was making a mixer or summer or subtractor or whatever, but none of those fit the bill, so i thought i had an extra degree of freedom somewhere
then i tried to calculate the transfer function but i got
>Va + Vb = 0
so it turns out i've got one less degree of freedom, do i need to do the calculation assuming non-infinite input resistance?