Curriculum › Grade 9 › Mathematics

Exponential Growth Wins

  • Grade 9
  • Mathematics
  • F-LE.A.3
  • Functions
  • Free lesson

Aligned to F-LE.A.3 — Common Core State Standards for Mathematics.

What this lesson teaches

A quantity growing exponentially will eventually overtake any quantity growing linearly, quadratically, or as a polynomial, no matter how large the other one starts. The repeated multiplying compounds quickly.

Worked examples

Example 1

Compare f(x) = 2^x and g(x) = 10x. At x = 4, f = 16 and g = 40, so g leads. But at x = 7, f = 128 and g = 70 — the exponential has passed the linear.

Example 2

Even a slow exponential wins: 1.01^x eventually passes 1000x, just not until x is in the thousands.

Example 3

A quadratic also loses to an exponential. x^100 is beaten by 2^x, far out, which is why 'polynomial time' matters in computing.

Practice questions

  1. Compare 2^x and 5x at x = 5.
  2. Which is larger at x = 10: 2^x or x^2?
  3. Explain in words why doubling beats adding a fixed amount over time.

Watch the lesson

Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.

▶ Watch this lesson

En español

El Crecimiento Exponencial Gana

Una cantidad que crece de forma exponencial terminará por superar a cualquier cantidad que crezca de forma lineal, cuadrática o polinomial, sin importar qué tan grande empiece la otra. La multiplicación repetida se acumula rápido.

Ejemplo 1: Compara f(x) = 2^x y g(x) = 10x. En x = 4, f = 16 y g = 40, así que g va adelante. Pero en x = 7, f = 128 y g = 70: la exponencial ya pasó a la lineal.

Ejemplo 2: Hasta una exponencial lenta gana: 1.01^x acaba rebasando a 1000x, solo que no hasta que x llega a los miles.

Ejemplo 3: Una cuadrática también pierde contra una exponencial. x^100 es superada por 2^x, muy lejos, por eso importa el 'tiempo polinomial' en computación.

More Functions lessons

Interpreting Graphs of FunctionsF-IF.B.4What Is a Function?F-IF.A.1Evaluating FunctionsF-IF.A.2Sequences as FunctionsF-IF.A.3Domain in ContextF-IF.B.5Average Rate of ChangeF-IF.B.6

Teach this lesson today

An AI tutor that guides with questions instead of just giving answers — all K–12 core subjects, every child in the family.

Start free — no card required