Math lesson plan · 9th grade (Year 10 in England) · 45 minutes
Multiply a polynomial by a monomial
Algebra
CCSS HSA.APR.A.1England: GCSE Foundation Algebra
Objective and success criteria
Students will: Multiply a polynomial by a monomial.
- 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: Expand brackets (distributive property); Multiply monomials using exponent laws
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 (Expand brackets (distributive property); Multiply monomials using exponent laws). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Expand: 3(x + 2) → 3x+6Prompt: Multiply every term inside the bracket by the number outside.
- Simplify: (6x⁵)(5x⁴) → 30x^9Prompt: Multiply the numbers.
- Expand: −7(4x + 9) → -28x-63Prompt: The negative outside multiplies every term inside.
Hook · 5 min
- Show a "think of a number" puzzle and ask the class to work out the starting number.
- Share the objective: Multiply a polynomial by a monomial. 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: Expand: 6x(4x² − 6x + 4)
- Step 1: 24x³ − 36x² + 24x
- Answer: 24x^3-36x^2+24x
- 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.
- Expand: 2x(−6x² − 9x + 1) → -12x^3-18x^2+2xPrompt: Multiply every term inside the bracket by the term outside.
- Expand: −4x³(5x² − 6x − 1) → -20x^5+24x^4+4x^3Prompt: Multiply the numbers and add the exponents for each term.
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.
- Diego expanded −5x(6x − 7) and got −30x² − 35x. What should the answer be? (−30x² − 7 / 30x² − 35x / −30x² + 35x / −30x + 35) → −30x² + 35xPrompt: Multiply −5x by each term, sign included.
- Expand: 3x²(4x² − 2x − 3) → 12x^4-6x^3-9x^2Prompt: Multiply the numbers and add the exponents for each term.
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: Expand brackets (distributive property).
- 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-9.
Free lesson plan from eurekami.com/lesson-plan-builder