  We construct an explicit projective bimodule resolution for the Leavitt path
algebra of a row-finite quiver. We prove that the Leavitt path algebra of a
row-countable quiver has Hochschild cohomolgical dimension at most one, that
is, it is quasi-free in the sense of Cuntz-Quillen. The construction of the
resolution relies on an explicit derivation of the Leavitt path algebra.
