Asfaw, Teffera M.2022-03-212022-03-212022-03-17Teffera M. Asfaw, “A Positive Answer on Nirenberg’s Problem on Expansive Mappings in Hilbert Spaces,” Abstract and Applied Analysis, vol. 2022, Article ID 9487405, 5 pages, 2022. doi:10.1155/2022/9487405http://hdl.handle.net/10919/109362Nirenberg proposed a problem as to whether or not a continuous and expansive operator T : X⟶X (where X is a Hilbert space) is surjective if R(T)∘ ≠∅. I shall give a positive answer for the problem provided that R(T)∘ is unbounded. For contents related to this paper, the reader is referred to the remarks and the study of Asfaw (2021). The present paper gives a complete answer for the problem that has been open for about 47 years.application/pdfenCreative Commons Attribution 4.0 InternationalArticle - Refereed2022-03-20Copyright © 2022 Teffera M. Asfaw. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.https://doi.org/10.1155/2022/9487405