# Difference of square no.s

1. Sep 14, 2008

### chhitiz

is there an expression for the difference of two square no.s, except, of course for rsquare minus ssquare

2. Sep 14, 2008

### huba

(r+s)(r-s)

3. Sep 14, 2008

### chhitiz

god you are funny. i posted this question because i was trying to find out all possible no.s which have a self-conjugating ferrer's graph, and needed to see if diff. of two square no.s is in anyway in form of a triangle no. or not. anyways, i have inferred that all no.s except for 2 can be jotted as a self-conjugating ferrer's graph. am i correct?

4. Sep 14, 2008

### CRGreathouse

Your first post was entirely unclear, and I'm not quite sure what your second means. "if diff. of two square no.s is in anyway in form of a triangle no. or not"? Does that mean something like "Is the difference of two squares triangular?"?

If that interpretation is generally correct, I can think of at least four ways to take it:
$$\forall n>m \exists t:t(t+1)/2=n^2-m^2$$
$$\forall n \exists m,t:t(t+1)/2=n^2-m^2$$
$$\forall N \exists n>m>N,t:t(t+1)/2=n^2-m^2$$
$$\exists n,m,t:t(t+1)/2=n^2-m^2$$

If it's not, then you'll have to be more clear.

5. Sep 15, 2008

### chhitiz

that was exactly what i meant, so thanks

6. Sep 15, 2008

### CRGreathouse

Which?

7. Sep 15, 2008

### chhitiz

the first one. by the way, am i not correct in saying that all +ve integers except 2 can be expressed as a self conjugating ferrer's graph?

8. Sep 15, 2008

### CRGreathouse

The first few (n, m) for which this fails are:
(3, 1)
(5, 1)
(3, 2)
(4, 2)
(4, 3)
(5, 3)
(5, 4)