M4.10.1 For the adult
Function notation
My book says f(x) = 2x − 1. Is f a number that multiplies x?
What this chapter teaches
A function is a rule with one output for each input. f(x) = 2x − 1 names the rule f. The brackets hold the input, and f(3) means put 3 into the rule. The equation f(x) = 7 turns this round: the output is known and the input is wanted, so undo the rule step by step.
Three questions to ask
There is no one right wording. Listen for the idea.
- How do you work out f(3) when f(x) = 2x − 1?
- What is the difference between finding f(7) and solving f(x) = 7?
- How can you read f(3) from the graph of y = f(x)?
After the chapter, the learner can
- Find f(3) when f(x) = 2x − 1
- Solve f(x) = 7 for the same function
What they copy into their notebook
A function is a rule. Each input has one output. f(3) means put 3 in. f(x) = 7 means find the x that gives 7. Undo the rule backwards.