(a) The district boundaries may be expanded or territory may be annexed to the district under this subchapter only if the expansion or annexation, the assumption of debt, and the imposition of taxes are approved by a majority of the voters voting at:
(1) an election held in the district; and
(2) a separate election held in the territory to be added.
(b) If the election results for an election under this subchapter are not favorable to the proposition to expand the district or to annex the territory, subsequent elections may be held on the same issue.