# Quadratic again. may be tricky

1. Nov 28, 2007

### mathusers

hi, i think this one is a bit trickier.

for an odd prime number "p", let $F_p$ be the field with "p" elements. i.e. the integers {0,....p-1} with addition and multiplication defined modulo "p".
So how many quadratic forms are there on the vector space $F^n_p$ and why?

Last edited: Nov 28, 2007
2. Dec 1, 2007

### CompuChip

Can you write down the general form of such a quadratic form?
E.g., for n = 1, 2, 3 it would be
$$a x^2; \quad a x^2 + b x y + c y^2; \quad a x^2 + b x y + c x z + d y^2 + e y z + f z^2$$ --
do you know of a general formula?

(By the way, you probably don't need the general formula, just the number of terms occurring in it. So in the above example, 1, 3 and 6 respectively).