When radioactive substances decay, the amount remaining will form a geometric sequence when measured over constant intervals of time. The table shows the amount of a radioactive isotope initially and after 2 hours. What are the amounts left after 1 hour, 3 hours, and 4 hours? Hours Elapsed: 0 1 2 3 4. Grams of the isotope: 1866 __ 471 __ __ please HELP!