Factorising and Solving Quadratics

From the study guide

Course Outline

  1. Common Factors and Grouping
  2. Factoring Quadratic Expressions
  3. Special Products and Cubics
  4. Quadratic Equations by Factoring
  5. The Quadratic Formula
  6. Completing the Square
  7. Quadratic Models and Applications
  8. Linear–Nonlinear Systems
  9. Mathematicians and Applications

1. Common Factors and Grouping

Key Concepts & Definitions

  • Factorising: The reverse of expanding, writing an expression as a product of factors by taking out common factors.

★ Must-know

📌 A factorisation is complete only when all common factors have been taken outside the brackets.

  • 🔄 Factorise by grouping in these steps:
    1. Pair terms so each pair has a common factor
    2. Factor each pair
    3. Take out the common bracket

Further detail

  • The expression ah+ak+bh+bkah+ak+bh+bk factorises by grouping as (h+k)(a+b)(h+k)(a+b).

2. Factoring Quadratic Expressions

  • For a monic quadratic x2+bx+cx^2+bx+c, find two numbers whose product is cc and whose sum is bb, then use them as the constants in the two factors.
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Practice quiz preview

1. A student changes 5x+105x+10 into 5(x+2)5(x+2). Which operation has the student performed?

2. A student writes 12y2+18y=3y(4y+6)12y^2+18y=3y(4y+6). What change is needed to make the factorisation complete?

3. To factorise 6px+9py+4qx+6qy6px+9py+4qx+6qy by grouping, which sequence should be used?

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Flashcard preview

What does factorising do to an expression?

It writes the expression as a product of factors by taking out common factors.

When is a factorisation complete?

When all common factors have been taken outside the brackets.

What is the sequence for factorising by grouping?

Pair terms with common factors, factor each pair, then take out the common bracket.

How do you factor a monic quadratic x2+bx+cx^2+bx+c using two numbers?

Find numbers with product cc and sum bb, then use them as the factor constants.

For ax2+bx+cax^2+bx+c with a≠1a\ne1, what product and sum guide the split-middle-term method?

The two numbers have product acac and sum bb.

After splitting the middle term in ax2+bx+cax^2+bx+c, what does the grouping method factor out?

The common bracket.

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Frequently asked questions

What does the Factorising and Solving Quadratics study guide cover?

It covers the core concepts of Factorising and Solving Quadratics, organized by topic with the key definitions, explanations and takeaways, so it's easier to learn and remember.

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How many questions are in the Factorising and Solving Quadratics quiz?

The practice quiz has 20 multiple-choice questions, each with an explanation. Use it to check what you know and find your gaps.

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How do I study Factorising and Solving Quadratics with flashcards?

There are 45 flashcards on Factorising and Solving Quadratics, with a question on the front and the answer on the back. Try to recall each answer before you flip, and let spaced repetition bring back the ones you miss.

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