1. The problem statement, all variables and given/known data Nuclei of radioactive element A are produced at rate t^2 (where t is time) at any time t. The element A has decay constant λ. Let N be the number of nuclei of element A at any time t. At time t=t0, N is minimum. Then N at t0 is what? 3. The attempt at a solution [itex]N(t) = kt^2 - \lambda t [/itex] For N to be minimum, dN/dt = 0. But doing this gives me the wrong answer.