Barton Willis wrote: >> >> And one more question about substitution and assupmtion: >> I need to assume that f(x) >> r(x) + t(x). I.e. that f(x) + r(x) + t(x) > ~= >> f(x), and f(x) - r(x) - t(x) ~=f(x). > > What does >> and ~= mean? I read >> as meaning much greater than, and ~= as approximately equal to. Ray