MODULE 01 · LESSON 01
Functions
A function is one rule that turns each allowed input into one output.
PLAIN-LANGUAGE INTRODUCTION
What is this?
A function is one rule that turns each allowed input into one output.
One simple example
Use f(x) = 2x + 1. For x = 3, the output is 7.
What goes in?
One allowed value. Here, x is 3.
What comes out?
The rule’s result. Here, f(3) is 7.
Why does it matter?
Models are functions with adjustable numbers inside their rules.
What is it not?
A function is not a list of guesses. Its rule fixes each output.
WORK THROUGH THE IDEA
See the idea in more detail
- The symbol
fnames the function. The symbolxnames its input. - Send in
x = 3. The rule says to multiply by2, then add1. - First compute
2 × 3 = 6. Then compute6 + 1 = 7. - So
f(3) = 7. The plotted points show the same rule for four inputs. - Common mistake:
f(x)does not meanf × x. It means the output fromf.