← Day 11
UNIT 6 / 8 · LESSON 1 / 4 · 24 MINUTES

Treat a function as an input-output rule

Function notation tells you which input to use. It does not mean multiply f by x.

01 / THE METHOD

Make it repeatable

  1. Identify the input inside the parentheses.
  2. Substitute it wherever x appears.
  3. Simplify using order of operations.
  4. If asked for an inverse relationship, work backward from the output.
02 / WORKED EXAMPLE

Watch the method in action

If f(x) = 3x² − 2, find f(−2).
  1. Substitute −2 for x.
  2. Square first: (−2)² = 4.
  3. Compute 3(4) − 2 = 10.

f(−2) = 10.

03 / QUICK CHECK

Try it yourself

What is f(−2)?

04 / PRACTISE AND CHECK

Apply the method to real questions

Start with guided questions and feedback. Then take a fresh independent set without hints. Reach at least 80% on that set to record this lesson.

Pass the quick check above to unlock practice.