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  1. ← All courses
  2. Precalculus
  3. Unit 5: Quadratics

Lesson 2 of 5

Factoring trinomials

Use sum-product pairs, AC splitting, grouping, and the zero-product rule.

Subject to changeOptional future study, outside the current course sequence. This lesson and its homework preview are unassigned and may change.

Lessons and study tools
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Current units

  1. Unit 1: Essential Review
    1. Find a starting point
    2. Evaluate and compare expressions
    3. Read powers and multiply expressions
    4. Solve equations and describe intervals
    5. Essential algebra review
  2. Unit 2: Functions
    1. Read and use function notation
    2. Combine functions in the right order
    3. Keep inputs and outputs allowed
    4. Describe change and graph behavior
    5. Reverse a function safely
    6. Use symmetry to compare inputs
    7. Functions review
  3. Unit 3: Linear Functions
    1. Build a model with constant change
    2. Write and compare line equations
    3. Reverse a linear model
    4. Build and read piecewise rules
    5. Linear functions review
Optional future study · Subject to change

Unassigned previews outside the current course sequence.

  1. Unit 4: Exponential Functions · Optional future study · Subject to change
    1. Simplify with exponent laws
    2. Interpret rational exponents over the reals
    3. Build repeated-factor models
    4. Solve equations with a common base
    5. Read exponential graphs and their limits
    6. Exponentials review
  2. Unit 5: Quadratics · Optional future study · Subject to change
    1. Factoring patterns
    2. Current lessonFactoring trinomials
    3. Completing the square
    4. Quadratic models
    5. Linear quadratic systems
    6. Quadratics review
  3. Unit 6: Transformations · Optional future study · Subject to change
    1. Shifts and reflections
    2. Stretches and compressions
    3. Move and reshape a function
    4. Transformations review
  4. Unit 7: Polynomials · Optional future study · Subject to change
    1. Polynomial structure
    2. Polynomial behavior
    3. Polynomial graphs
    4. Polynomials review
  5. Unit 8: Rational Functions · Optional future study · Subject to change
    1. Simplify rational functions safely
    2. Divide polynomials and check remainders
    3. Combine rational expressions
    4. Solve rational equations and check candidates
    5. Rational expressions and equations review
  6. Unit 9: Trigonometry · Optional future study · Subject to change
    1. Right-triangle models
    2. Radians and circular arcs
    3. The unit circle
    4. Trigonometric identities
    5. Linear trigonometric equations
    6. Trigonometry review
  7. Unit 10: Trigonometric Graphs · Optional future study · Subject to change
    1. Sine and cosine models
    2. Period, frequency, and phase
    3. Build a sine or cosine model
    4. Sine and cosine graphs review
  1. 1Learn it
  2. 2Practice it
  3. 3Homework
  4. 4Finish

Step 1 of 4: Learn it

Learn it · 1 of 8Do Now · EasyNext: Build the ideaChoose an activity

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Worked example · 1 of 8

Worked example

Do Now · Easy

Do this: Try this on paper, then compare with the worked check.

Key words

  • Key word · Unit 5Zero product lawIf a product is zero, at least one factor must be zero.Exactly: For real numbers a,b, ab=0 implies a=0 or b=0.Mix-up alert: Make one side zero before using this law; it does not apply to a product equal to 6.See this in Key words

Factor x2+5x+6. Check: 2 and 3 multiply to 6 and add to 5, so the factors are (x+2)(x+3).

Big ideas

Build the idea

Do this: Read each idea, then say it in your own words.

  1. 1

    1. Sum and product

    For a trinomial x2+bx+c, seek p+q=b and pq=c. Then the factorization is (x+p)(x+q), checked by expansion.

  2. 2

    2. Split with AC

    For ax2+bx+c, the AC method seeks p+q=b and pq=ac. Split bx into px+qx, then factor by grouping; take out a GCF first.

  3. 3

    3. Grouping makes a common binomial

    In grouping, factor each pair of terms so the remaining binomial matches. A negative GCF may be needed to make both binomials identical.

  4. 4

    4. Zero-product rule

    If a product equals zero, at least one factor is zero. First make one side of an equation zero; factors of an expression alone are not solutions until an equation is specified.

Worked example

Guided practice · Medium

Do this: Cover each worked step and try it on paper before reading on.

Factor 6x2+11x+3. The AC product is 18 and the split is 9x+2x. Group to get 3x(2x+3)+(2x+3)=(3x+1)(2x+3). Expansion restores all three coefficients.

Step-through

Follow one checked example

Do this: Move through the four steps and check each number.

Factor 6x2+11x+3 using AC.

1. Given2. Represent3. Solve4. Check

Whole picture, 4 steps

4 steps. Tap a number or Show me how it works.

Worked example

A negative constant

Do this: Follow each step on paper before reading the result.

  1. Step 1: Factor x2−x−20.
  2. Step 2: Find a pair with product -20 and sum -1: -5 and 4.
  3. Step 3: Write (x−5)(x+4).
  4. Step 4: Expanding returns x2−x−20.

Worked example

Solve after moving terms

Do this: Follow each step on paper before reading the result.

  1. Step 1: Solve x2+2x=15.
  2. Step 2: Move 15 left: x2+2x−15=0.
  3. Step 3: Factor (x+5)(x−3)=0.
  4. Step 4: x=−5 or x=3; both satisfy the original equation.

Mix-up alert

Common mistake

Do this: Explain the wrong idea and the repair.

Wrong idea: factors can be set equal to zero when the product equals 12. Repair: the zero-product rule requires zero. Rearrange the equation first, then factor the resulting expression.

Watch

Video: Factoring trinomials

Do this: Watch the public lesson, pause to try a step, then return to your practice.

Watch on YouTubeOpens in a new tab. Keep your work here.

Watch for:

  • Finding factors whose product and sum match the trinomial.
  • Pause before a worked step and try it on paper. Compare the reasoning, not just the final answer.
Open on YouTube↗ (opens in a new tab)

From The Organic Chemistry Tutor · Factoring Trinomials - Quick & Simple

The linked video is free to watch. The creator may offer optional paid resources; they are not needed for this lesson. If YouTube is blocked, use the lesson notes and worked examples here.

Step 2 of 4: Practice it

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Flashcards

Recall and explain

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Card 1 of 8

Factoring trinomials

0 Know it0 Still learning

Expand (x+p)(x+q).

Deck options
Keyboard help

On the card: Enter or Space flips. Left and Right move. After revealing, 1 marks Still learning and 2 marks Know it. Tab reaches every control.

Question

For x2+bx+c, what must p and q satisfy?

Answer

p+q=b and pq=c.

Question

What product is used in the AC method?

Answer

a times c.

Question

What is the sum condition in AC?

Answer

p+q=b.

Question

Factor x2−3x−10.

Answer

(x-5)(x+2).

Question

Factor 2x2+7x+3.

Answer

(2x+1)(x+3).

Question

What does AB=0 imply over the reals?

Answer

A=0 or B=0, or both.

Question

Does every integer-coefficient quadratic factor over integers?

Answer

No. State the intended coefficient set.

Question

How do you check grouped factors?

Answer

Expand and compare all coefficients.

True or false

Test the statements

Do this: Decide true or false, then read why.

Statement 1 of 4

(x−2)(x+7)=x2+5x−14.

Self-test

Practice set 1

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6 questions. One at a time.

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Self-test

Practice set 2

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6 questions. One at a time.

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Write it

Explain your reasoning

Do this: Write a short explanation, then compare it with the model.

Step 1 of 3: Write

Use AC to factor 6x2−x−2 and solve 6x2−x−2=0.

0 words · Aim for 20 or more. This is a guide, not a limit.

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Write it

Optional challenge · Hard

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Step 1 of 3: Write

Solve 2x2+x−6=0 by factoring and check both roots without dropping the leading coefficient.

Start here if it helps: I can connect the conditions by...

0 words · Aim for 24 or more. This is a guide, not a limit.

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Match

Match the key words

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Word match round

Connect the ideas

0 / 4 connected

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Terms

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Step 3 of 4: Homework

Subject to changeOptional preview. This page does not mean this homework is assigned. Only turn it in if your teacher asks.

Optional practice preview · 3 points if assigned

Factoring trinomials practice preview

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Step 4 of 4: Finish

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Next lesson: Completing the squareUnit 5: Quadratics
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Published with approval from Mr. Farzin Khan Shifat. Last updated October 31, 2026.