let V be non empty right_complementable add-associative right_zeroed addLoopStr ; :: thesis: for v, u being Element of V holds (v + u) - u = v
let v, u be Element of V; :: thesis: (v + u) - u = v
thus (v + u) - u = v + (u - u) by RLVECT_1:28
.= v + (0. V) by RLVECT_1:5
.= v ; :: thesis: verum