help with algebra :( - Page 2

On September 30 2009 06:25 IMlemon wrote:


Problem with this, is that it's not a valid formula in mathematical logic. Can you use predicates? If so, something like this would do.

P(x) - number is real
R(x) - number is positive
Q(x,y) - y is smaller than x

F = ∀x∃y (P(x) /\ P(y) /\ R(x) /\ R(y) /\ Q(x,y))

^True if x is positive and real, false otherwise. y must be kept in check too.

If you can't use predicates, im kinda out of ideas how to express it precisely. To state that x ∈ R you'd have to write out all of the real numbers' properties.