Year 11 Function Notation, Composites and Inverses Worksheet — Level 3 — Answers
Answer sheet with worked solutions for the Year 11 functions worksheet.
Year 11 Function Notation, Composites and Inverses Worksheet — Level 3 — Answers
f(x) notation means "the value of the function at x". For a composite, substitute the inner function into the outer one. For an inverse, swap x and y and solve for y.
1.Find the inverse function of f(x) = −x + 6.
Answer: f−1(x) = −x + 6
- y = −x + 6
- Swap x and y: x = −y + 6
- Solve for y: y = −x + 6
2.Find the inverse function of f(x) = −5x − 6.
Answer: f−1(x) =
- y = −5x − 6
- Swap x and y: x = −5y − 6
- Solve for y: y =
3.Find the inverse function of f(x) = 5x + 3.
Answer: f−1(x) =
- y = 5x + 3
- Swap x and y: x = 5y + 3
- Solve for y: y =
4.f(x) = x + 6 and g(x) = −3x − 1. Find g(f(x)) in simplest form.
Answer: −3x − 19
- g(f(x)) = −3(x + 6) − 1
- = −3x − 19
5.f(x) = x + 3 and g(x) = 4x + 6. Find g(f(x)) in simplest form.
Answer: 4x + 18
- g(f(x)) = 4(x + 3) + 6
- = 4x + 18
6.f(x) = 2x + 6 and g(x) = −x − 6. Find g(f(x)) in simplest form.
Answer: −2x − 12
- g(f(x)) = −1(2x + 6) − 6
- = −2x − 12
7.f(x) = −2x + 1 and g(x) = 3x − 2. Find f(g(x)) in simplest form.
Answer: −6x + 5
- f(g(x)) = −2(3x − 2) + 1
- = −6x + 5
8.Find the inverse function of f(x) = 4x − 3.
Answer: f−1(x) =
- y = 4x − 3
- Swap x and y: x = 4y − 3
- Solve for y: y =
9.f(x) = 4x − 5 and g(x) = 5x + 5. Find f(g(x)) in simplest form.
Answer: 20x + 15
- f(g(x)) = 4(5x + 5) − 5
- = 20x + 15
10.f(x) = 2x − 2 and g(x) = −x + 2. Find f(g(x)) in simplest form.
Answer: −2x + 2
- f(g(x)) = 2(−x + 2) − 2
- = −2x + 2
11.f(x) = −4x − 5 and g(x) = 3x − 6. Find f(g(x)) in simplest form.
Answer: −12x + 19
- f(g(x)) = −4(3x − 6) − 5
- = −12x + 19
12.f(x) = 5x − 6 and g(x) = −3x. Find g(f(x)) in simplest form.
Answer: −15x + 18
- g(f(x)) = −3(5x − 6)
- = −15x + 18
Marking tips
- Give credit for correct method even when the final answer slips — the working shows where the thinking went right.
- For open-ended tasks, use the success criteria as a checklist rather than looking for one "right" answer.
- Celebrate what went well first, then pick one thing to work on next.