The expression 1 + e^-x combines a constant and an exponential function. Here, e represents Euler's number, approximately equal to 2.718, and x is a variable. The term e^-x decreases as x increases, approaching zero but never reaching it. This means that as x becomes very large, the expression approaches 1. In this context, 1 + e^-x is often used in mathematics and statistics, particularly in logistic functions and probability distributions. It helps model situations where a quantity approaches a limit, such as population growth or the spread of diseases, making it a valuable tool in fields like biology and economics.