The group IA(Fn) is the kernel of the natural homomorphism . Magnus showed in [M] that these groups are finitely generated and later asked about their finite presentability. In  we prove that IA(F3) is not finitely presentable. The paper utilizes a known homomorphism , and as a by-product gives non-finite presentability of for every group that maps homomorphicaly onto the infinite cycle. The heart of the proof is an analysis of relations in the group GL2(k[t,t-1]) where k is a (finite) field. By a theorem of Stuhler [S], these groups are not finitely presentable, but we needed a stronger result. We obtained an alternative proof in  by utilizing a complex that we constructed for arbitrary rings R and proved its contractibility when R=k[t,t-1]. The complex is analogous to the unstable Volodin complex (foundations of Algebraic K-theory) and is probably of more general interest. For example, there is an exact sequence , where GEU2stands for Sylvester's ``general elementary universal'' group. Finally, for many rings R, we construct in  homomorphisms from SL2(R[x]) onto free groups of infinite rank, improving significantly the results of Grunewald-Mennicke-Vaserstein [GMV]. In  we prove non-finite presentability of GL3 and finite presentability of GLn for large classes of rings, improving results of several authors.