Study Guide

Dilations and scale factor

You are learning dilations and scale factor in Geometry · Honors (Similarity). Focus: Perform dilations; relate scale factor to corresponding lengths.

What this standard means

Add, subtract, and multiply polynomials with correct like terms
Factor with GCF and simple trinomials or special products
Use factors to find zeros when graphing
Expand and factor as inverse processes on a check problem
Explain degree and leading-term end-behavior cues when relevant

How to use the 20 practice sets

| Sets | When to use | | --- | --- | | 1–5 | First week — explore together; short items on Dilations and scale factor | | 6–10 | Core practice — main representations and fluent written work | | 11–15 | Mixed review — explain thinking; mix problem types for 3.1 | | 16–20 | Stretch — multi-step / word problems and mastery tasks |

Pacing: 10–15 minutes per session. Praise clear explanations, not speed alone.

How to practice (10–15 minutes)

1. Warm up with one short item on dilations and scale factor. 2. Write a one-sentence plan before computing. 3. Show organized steps and box the final answer. 4. Check with substitution, a diagram, or an estimate. 5. Explain one sticky step in your own words.

Teacher quick-use (5 minutes)

1. Warm-up: class uses organize like terms, then factor or expand on one easy 3.1 item (board or oral). 2. Guided: name the method, try one item together, and have students point to each key step. 3. Independent: partners try a short dilations and scale factor item from Practice sets 1–5. 4. Exit: each student whispers to a partner one sticky spot for 3.1 today.

Progress checklist for students

Mark when it is mostly true on two different days:

[ ] Add, subtract, and multiply polynomials with correct like terms
[ ] Factor with GCF and simple trinomials or special products
[ ] Use factors to find zeros when graphing
[ ] Expand and factor as inverse processes on a check problem

Map to practice bands: sets 1–5 → early checks; sets 6–10 → core dilations and scale factor; sets 11–20 → mixed and stretch.

Common misconceptions

Address these early. Name the misconception, show a correct model, then have students retry a short item.

Combining unlike terms — See Common Mistakes for diagnosis and repair steps.
Forgetting the GCF before other factoring — See Common Mistakes for diagnosis and repair steps.
FOIL / distribution mistakes — See Common Mistakes for diagnosis and repair steps.
Assuming every trinomial factors over the integers — See Common Mistakes for diagnosis and repair steps.

Quick checks

Use as 2–5 minute formative checks mid-lesson. Students should finish independently when possible.

1. Write one clean example that shows you understand dilations and scale factor. 2. True or false / spot-the-error: invent a common slip for 3.1 and fix it. 3. In one sentence, name the method you used (organize like terms, then factor or expand).

Exit tickets

End-of-lesson evidence of learning. Collect, sort into got-it / almost / reteach, and plan the next day.

1. Solve a short dilations and scale factor item and box the answer with units if needed. 2. In one sentence: What rule or idea did you use for 3.1?

Challenge problems

Stretch tasks for students ready for more complexity after core practice.

1. Create a multi-step problem that uses dilations and scale factor and one idea from Similarity. Solve it. 2. Find and fix an error: write a wrong solution for 3.1, then correct it with reasons.

Enrichment questions

Open-ended extensions that deepen understanding and connections across topics.

1. How does dilations and scale factor help with other topics in Similarity? 2. Connect Dilations and scale factor to Apply AA and SAS similarity: what stays the same and what changes?

Math talk prompts

Use for turn-and-talk, whole-class discussion, or written reflection.

What is the ask in your own words?
How does organize like terms, then factor or expand help you on this topic?
What would happen if we skipped a required condition of 3.1?
How do you know your answer matches the question?
What do the key features mean in this context?

Vocabulary review

Revisit these terms with examples, non-examples, and student-friendly definitions.

polynomial — A sum of terms with nonnegative integer powers of a variable.
like terms — Terms with identical variable powers that can be combined.
GCF — Greatest common factor shared by all terms.
factor — Rewrite as a product; zeros often come from factors set to zero.

Review and practice tests

1. Start Review 1/10 when sets 1–3 feel comfortable. 2. Move up one level when a review is completed with little help. 3. Use Practice Test 4/10–6/10 for mid-topic check-ins. 4. Practice Test 10/10 is the mastery bar for 3.1.

[ ] Add, subtract, and multiply polynomials with correct like terms
[ ] Factor with GCF and simple trinomials or special products
[ ] Use factors to find zeros when graphing

See also Exam Strategy for readiness and test-day moves on this topic.

Materials for this standard

Parent Guide — home language, connections, try-together tasks
Exam Strategy — quiz / unit-test prep and traps
Common Mistakes — diagnoses and fixes for this topic
Practice Problems — 20 printable sets
Word Problems / Mixed Practice — additional practice bands
Review — 10 difficulty levels (1/10 easiest → 10/10 stretch)
Practice Test — 10 difficulty levels for progress checks
Answer key — step-by-step solutions
Interactive — quiz, mixed quiz, flashcards, typed practice sets