Math lesson plan · 8th grade (Year 9 in England) · 45 minutes
Write a linear function rule from a table
Algebra
CCSS 8.F.B.4England: KS3 AlgebraEngland: GCSE Foundation Algebra
Objective and success criteria
Students will: Write a linear function rule from a table.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Find the rate of change from a table; Find the y-intercept from an equation, table or graph
Leads to: the next skill in this area.
Materials: Balance scales or a balance drawing, Algebra tiles, Function machine cards, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Find the rate of change from a table; Find the y-intercept from an equation, table or graph). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- x: 2, 7, 12, 17. y: 21, 51, 81, 111. What is the rate of change (slope)? → 6Prompt: How much does y change each time x changes?
- What is the y-intercept of y = −1 − 3x? → -1Prompt: The y-intercept is the value of y when x = 0.
- x: 0, 2, 4, 6. y: 1, 2, 3, 4. Find the slope. Give a fraction in simplest form. → 1/2Prompt: Slope = change in y ÷ change in x.
Hook · 5 min
- Show a "think of a number" puzzle and ask the class to work out the starting number.
- Share the objective: Write a linear function rule from a table. Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: x: 0, 1, 2, 3. y: −8, −13, −18, −23. Write y in terms of x. Type the right-hand side.
- Step 1: b = −8, m = −5
- Step 2: y = −5x − 8
- Answer: -5x-8
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- x: 0, 1, 2, 3. y: −8, −4, 0, 4. Write y in terms of x. Type the right-hand side. → 4x-8Prompt: The value at x = 0 is the y-intercept.
- x: 2, 4, 6, 8. y: 4, −2, −8, −14. Write y in terms of x. Type the right-hand side. → -3x+10Prompt: x goes up in 2s, so halve the change in y to get the slope.
You do: independent practice · 10 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- x: 0, 1, 2, 3. y: −4, −6, −8, −10. Write y in terms of x. Type the right-hand side. → -2x-4Prompt: The value at x = 0 is the y-intercept.
- x: 2, 4, 6, 8. y: −5, −15, −25, −35. Write y in terms of x. Type the right-hand side. → -5x+5Prompt: x goes up in 2s, so halve the change in y to get the slope.
Watch out for
- Doing an operation to one side of an equation but not the other.
- Reading 3x as 3 + x, or thinking x always stands for one particular number.
Support and stretch
Support
- Review first: Find the rate of change from a table.
- Use concrete materials: balance scales or a balance drawing.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/math/grade-8.
Free lesson plan from eurekami.com/lesson-plan-builder