Difference of two squares
I can use the special case when the product of two binomials is the difference of two squares.
- Year 9
Difference of two squares
I can use the special case when the product of two binomials is the difference of two squares.
Lesson details
Key learning points
- The product of two binomials often produces three terms.
- There are cases where the coefficient of the linear term is zero.
- The terms in the two binomials can indicate this.
- You can use an area model to explore the structure.
Keywords
Partial product - A partial product refers to any of the multiplication results that lead up to an overall multiplication result.
Binomial - A binomial is an algebraic expression representing the sum or difference of exactly two unlike terms.
Common misconception
Squaring a binomial is the same as just squaring each term. This can then cause confusion with difference of two squares where expanding a pair of binomials does result in just two terms.
Using an area model and taking time to check the partial products each time, particularly with negative terms, should help students to check if they have expanded correctly.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.A zero pair is __________.
Q2.Use this area model to help you find the correct expansion of $$(x + 3)(x + 9)$$.
Q3.Use this area model to help you find the correct expansion of $$(x - 5)(x - 11)$$.
Q4.Fill in the missing value in this simplified expansion: $$(x +8)(x - 3)\equiv x^2 +$$ $$x - 24$$.
Q5.Which is the correct expanded form of $$(x - 6)^2$$ ?
Q6.Match each product of two binomials to its correct expansion.
$$(x+3)(x+2)$$ -Â $$x^2 + 5x + 6$$
$$(x+3)(x-2)$$ -Â $$x^2 + x - 6$$
$$(x+2)(x-3)$$ -Â $$x^2 - x - 6$$
$$(x-2)(x-3)$$ -Â $$x^2 - 5x + 6$$
$$(x - 6)(x + 1)$$ -Â $$x^2 - 5x - 6$$
$$(x + 6)(x -1)$$ -Â $$x^2 + 5x - 6$$
Assessment exit quiz
6 Questions
Q1.Match each product of two binomials to its simplified form.
$$(x + 8)(x + 8)$$ -Â $$x^2 + 16x + 64$$
$$(x + 8)(x - 8)$$ -Â $$x^2 - 64$$
$$(x - 8)(x - 8)$$ -Â $$x^2 - 16x + 64$$
Q2.Which of these expressions can be written as the difference of two squares?
Q3.Match each product of two binomials with its simplified form.
$$(x + 2)(x - 2)$$ -Â $$x^2 - 4$$
$$(2 + x)(2 - x)$$ -Â $$4 - x^2$$
$$(x + 4)(x - 4)$$ -Â $$x^2 - 16$$
$$(4 - x)(4 + x)$$ -Â $$16 - x^2$$
$$(x - 8)(x + 8)$$ -Â $$x^2 - 64$$
$$(8 - x)(8 + x)$$ -Â $$64 - x^2$$
Q4.Which of these show an expression written in the 'difference of two squares' form?
Q5.Which of these expressions can be written as the difference of two squares?
Q6.Expand $$(3y - 4)(3y + 4)$$.
