radioactive iodine decays according to the formula A(t)=A0×a^-t where A0 is the initial amount and t is time in days. find a, assuming the half life of radioactive iodine is 8 days. My route was: step 1) 1/2×A0 = A0×a^-t step 2) A0 cancels out step 3)1/2=a^-t. Step 4) Dont know where to go from here. The answer is a = 2^1/8 or about 1.09 How do I find this answer?