Integrated Math 1 / Unit 5: Exponential Functions and Geometric Sequences
5.5 Comparing Linear and Exponential Growth
Notes
Linear functions grow by a constant amount; exponential functions grow by a constant factor.
- Exponential growth eventually exceeds any linear function, even if it starts smaller.
- To identify a table: constant differences mean linear; constant ratios mean exponential.
- Example: $y = 4, 7, 10, 13$ has constant differences of 3, so it is linear.
- To compare, evaluate both functions at several inputs.
Practice
For large values of $x$, which grows faster?
Exponential growth eventually overtakes any linear function.
A table gives $y = 4, 7, 10, 13$ for $x = 0, 1, 2, 3$. What type of function is it?
The differences are all 3, so it is linear.
Let $f(x) = 50 + 10x$ and $g(x) = 2^x$. For whole numbers $x$, what is the least $x$ where $g(x)$ is greater than $f(x)$?
At $x = 6$: $64 < 110$. At $x = 7$: $128 > 120$.
Ready for more? Take the Unit 5 test.