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9th grade · Math · Unit 4 of 16

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.

Texas Essential Knowledge and Skills (TEKS) teks student expectation: A.2(A); A.12(A); A.12(B) · domain and range, deciding whether a relation is a function, 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 Texas

In the Texas Essential Knowledge and Skills (TEKS), this is unit 4 of 16 in 9th grade Math, after Lines & Intersections and before Multi-Step Equations.

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: Texas Education Agency (TEA)

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

    f(x) = −5x − 8. For which x is f(x) = −28?

    • 5
    • 4
    • -28
    • -4

  2. Question 2

    What is the range of {(−3, 2), (−1, 1), (2, 7), (4, 5)}?

    • {−3, −1, 2, 4}
    • {−3, −1, 1, 2, 4, 5, 7}
    • {2, 3, 6, 8}
    • {1, 2, 5, 7}

  3. Question 3

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

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

  4. Question 4

    If f(x) = −5x + 1, what is f(4)?

    answer box

  5. Question 5

    f(x) = −3x + 1. For which x is f(x) = −17?

    • -17
    • -6
    • 6
    • 7

  6. Question 6

    What is the domain of {(−3, 5), (0, 7), (1, −3), (4, 7)}?

    • {−2, 1, 2, 5}
    • {−3, 0, 1, 4}
    • {−3, 0, 1, 4, 5, 7}
    • {−3, 5, 7}

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