Hi,

I have a general question about whether you can usually use either formula, A(t) = Ae^(kt), or A(t) = Ab^t, in exponential decay (half-life) word problems, or if there is some difference in where each of these formulas is applicable. I'm used to using A(t) = Ae^(kt) for everything, but I saw some resources on the web and videos where A=Ab^t was used (also, A=A(1+r)^t)

For example, in this problem: "Radioactive iodine I 131 has a half life of 8 days . If you start with 20g of radioactive iodine, write a function for the grams of I131 after t days." Can you use either formula for this problem, and if so, would there be a preference?

Please let me know if I can provide any other information, and thank you!

~Kathy