What is the constant k in the form of solution y(t) = Aexp(kt)?

[beanryu]

In 440 days, an unknown radioactive substance decays to 30 percent of its original amount.


(a) What is the constant k in the form of solution y(t) = Aexp(kt)?

k=?

First of all... I don't even know what Aexp(kt) mean

does it A^(kt) or what?!

 

[dav2008]

It means y(t)=Ae^{kt}