Math lesson plan · 12th grade (Year 13 in England) · 30 minutes
Differentiate axⁿ with the power rule
Calculus
CCSS HSF.IF.B.6England: A-level Pure Mathematics
Objective and success criteria
Students will: Differentiate axⁿ with the power rule.
- 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: Differentiate from first principles; Laws of exponents (indices)
Leads to: Differentiate polynomials term by term; Differentiate negative and fractional powers; Integrate powers of x (indefinite integrals)
Materials: Graphing tool or graph paper, Scientific calculators, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 4 min
- Quick retrieval from earlier learning (Differentiate from first principles; Laws of exponents (indices)). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Simplify a⁷ × a² and write it as a to a single power. What is the power? → 9Prompt: Multiplying powers of the same base: add the exponents.
- For f(x) = x² + 3x, simplify (f(x + h) − f(x))/h. (2x + h + 3 / 2xh + h² / 2x + 3 / 2x + h² + 3) → 2x + h + 3Prompt: Expand f(x + h) = (x + h)² + b(x + h).
- Using first principles, f(x) = −4x² − 5x gives (f(x + h) − f(x))/h = −8x − 4h − 5. What is f′(x)? → -8x-5Prompt: f′(x) is the limit as h → 0.
Hook · 3 min
- Show a distance-time graph of a journey and ask how fast it was going at one exact moment.
- Share the objective: Differentiate axⁿ with the power rule. Read the success criteria together.
I do: model it · 7 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: Differentiate y = −4x².
- Step 1: dy/dx = -4 × 2x
- Step 2: = −8x
- Answer: -8*x^1
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 6 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- Differentiate y = −3x⁴. → -12*x^3Prompt: Multiply by the power, then reduce the power by 1.
- Arjun differentiated 2x² and wrote 4x³. What is the correct derivative? (2x / 4x³ / 4x) → 4xPrompt: The power goes down by one, not up.
You do: independent practice · 7 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 6 questions are on the student sheet below, with answers in the key.
Exit ticket · 3 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Differentiate y = 2x⁷. → 14*x^6Prompt: Multiply by the power, then reduce the power by 1.
- Kofi differentiated 9x³ and wrote 27x⁴. What is the correct derivative? (27x² / 27x⁴ / 18x² / 9x²) → 27x²Prompt: The power goes down by one, not up.
Watch out for
- Forgetting the constant of integration.
- Differentiating a product by multiplying the derivatives.
Support and stretch
Support
- Review first: Differentiate from first principles.
- Use concrete materials: graphing tool or graph paper.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Move on to: Differentiate polynomials term by term; Differentiate negative and fractional powers; Integrate powers of x (indefinite integrals).
- 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-12.
Free lesson plan from eurekami.com/lesson-plan-builder