Let $R$ be a polynomial ring in $N$ variables over an arbitrary field $K$ and
let $I$ be an ideal of $R$ generated by $n$ polynomials of degree at most 2. We
show that there is a bound on the projective dimension of $R/I$ that depends
only on $n$, and not on $N$.
It is proved that when R is a local ring of positive characteristic, $\phi$
is its Frobenius endomorphism, and some non-zero finite R-module has finite
flat dimension or finite injective dimension for the R-module structure induced
through $\phi$, then R is regular.