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9th grade · Math · Unit 16 of 18

Function Notation

f(x), domain and range

What your child practices

Evaluating and solving with function notation, and naming the domain and range of a function, including a sensible domain in a real situation.

Alabama Course of Study content standard: AIP.15; AIP.16 · functions as a mapping from domain to range, and function notation

How we explain it

Children can open this short lesson before they practice.

  1. f(x) is the output of f when the input is x.
  2. To find f(3), replace every x with 3.
  3. The domain is all the inputs. The range is all the outputs.

Example: f(x) = 2x − 5. What is f(4)? 2 × 4 − 5 = 8 − 5. Answer: 3

Function Notation in Alabama

In the Alabama Course of Study, this is unit 16 of 18 in 9th grade Math, after Two-Way Tables & Causation and before Solving Systems.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Alabama State Department of Education (ALSDE)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    If f(x) = −4x + 6, what is f(−1)?

    answer box

  2. Question 2

    f(x) = −2x − 5. For which x is f(x) = −3?

    • -1
    • -3
    • 0
    • 1

  3. Question 3

    P(w) = 15w gives pay for w whole weeks worked in a 10-week summer job. Which domain makes sense?

    • Whole numbers from 0 to 10
    • Negative whole numbers
    • All real numbers
    • Any number from 0 to 150

  4. Question 4

    What is the range of {(−3, 2), (0, 4), (5, 6), (7, 2)}?

    • {3, 5, 7}
    • {−3, 0, 5, 7}
    • {−3, 0, 2, 4, 5, 6, 7}
    • {2, 4, 6}

  5. Question 5

    P(w) = 15w gives pay for w whole weeks worked in a 10-week summer job. Which domain makes sense?

    • All real numbers
    • Whole numbers from 0 to 10
    • Negative whole numbers
    • Any number from 0 to 150

  6. Question 6

    f(x) = 3x + 1. For which x is f(x) = 7?

    • 2
    • 3
    • 7
    • -2

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