Key Idea: Exponential Function

An exponential function models situations where a quantity grows or decays by a constant percentage rate over equal intervals.

General Rule:

y=S(1±%/100)^x

• y = output (final amount)

• S = starting value (y-intercept)

• 1±%/100​ = growth or decay factor

• $x$ = input (usually time)

Why this matters for the SAT:

Exponential functions are common in word problems involving growth, decay, interest, and population. Recognizing the structure of the formula helps you quickly identify the starting value, rate, and how the quantity changes over time.