Math lesson plan · 12th grade (Year 13 in England) · 30 minutes
Estimate a limit from a table of values
Calculus
CCSS HSF.IF.A.2England: A-level Pure Mathematics
Objective and success criteria
Students will: Estimate a limit from a table of values.
- 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: Function notation
Leads to: Evaluate limits by substitution or by factorising
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 (Function notation). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- f(x) = 2x² − 4x + 5. Find f(2). → 5Prompt: Replace every x with 2.
- f(x) = −5x − 5. For what value of x is f(x) = −20? → x = 3Prompt: Set the expression equal to the value.
- f(x) = x² − 5x − 6. Find f(5). → -6Prompt: Replace every x with 5.
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: Estimate a limit from a table of values. 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: f(x) = (x² − 1)/(x − 1). It has no value at x = 1 itself. x: 0.9 | 0.99 | 0.999 | 1.001 | 1.01 | 1.1 f(x): 1.9 | 1.99 | 1.999 | 2.001 | 2.01 | 2.1 Estimate lim(x→1) f(x).
- Step 1: Both sides approach 2.
- Step 2: 2
- Answer: 2
- 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.
- f(x) = (x² − 16)/(x − 4). It has no value at x = 4 itself. x: 3.9 | 3.99 | 3.999 | 4.001 | 4.01 | 4.1 f(x): 7.9 | 7.99 | 7.999 | 8.001 | 8.01 | 8.1 Estimate lim(x→4) f(x). → 8Prompt: Look at the outputs as x gets closer from both sides.
- g(x) = (x³ + 1)/(x + 1). x: −1.1 | −1.01 | −1.001 | −0.999 | −0.99 | −0.9 g(x): 3.31 | 3.0301 | 3.003 | 2.997 | 2.9701 | 2.71 Estimate lim(x→−1) g(x). → 3Prompt: Ignore the value at the point itself; watch the trend.
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.
- f(x) = (x² − 25)/(x + 5). It has no value at x = −5 itself. x: −5.1 | −5.01 | −5.001 | −4.999 | −4.99 | −4.9 f(x): −10.1 | −10.01 | −10.001 | −9.999 | −9.99 | −9.9 Estimate lim(x→−5) f(x). → -10Prompt: Look at the outputs as x gets closer from both sides.
- g(x) = (x³ − 27)/(x − 3). x: 2.9 | 2.99 | 2.999 | 3.001 | 3.01 | 3.1 g(x): 26.11 | 26.9101 | 26.991 | 27.009 | 27.0901 | 27.91 Estimate lim(x→3) g(x). → 27Prompt: Ignore the value at the point itself; watch the trend.
Watch out for
- Forgetting the constant of integration.
- Differentiating a product by multiplying the derivatives.
Support and stretch
Support
- Review first: Function notation.
- 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: Evaluate limits by substitution or by factorising.
- 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