  This paper deals with some nonlinear problems which exponential and
biexponential decays are involved in. A proof of the quasiconvexity of the
error function in some of these problems of optimization is presented. This
proof is restricted to fitting observations by means of exponentials having the
form $f (t) = {\lambda}_1 \exp(kt) + {\lambda}_2.$ Based on its quasiconvexity,
we propose an algorithm to estimate the best approximation to each of these
decays. Besides, this algorithm does not require an initial guess.
