If you are using a second-hand textbook you need to activate the 16-character Mathematics Essential Units 1&2 reactivation code. This reactivation code cannot be activated without the 16-character code on the inside front cover of your second-hand textbook. The Interactive Textbook is available as a calendar-year subscription. Your subscription term is defined as follows: if activation occurs between January and July of this year, subscription concludes 31 December of this year. If activation occurs between August and December of this year, subscription concludes 31 December the following year.