The time th required for the solution y of the decay problem
y' = ky, k < 0, y(0) = y0
To reach one-half of its original value is called the half-life.
(a) Find the half-life th in terms of the decay rate k.
(b) Show that if the solution has value B at any time t1, then the solution will have the value B/2 at time t1 + th.