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Learn how to factor expressions using the difference of two squares and perfect square trinomials methods with the help of area models and rules.
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Chapter 5 Section 5 • Factoring Special Forms
Factoring Difference of Two Squares • Two ways • Area model • Rule
Factor 9x2 - 100 Area model: set up 9x2 – 100 9x2 + 0x – 100 Sum is 0, product is - 900 Two numbers are 30 and - 30
Factor 9x2 - 100 Rewrite as the difference of two squares 9x2 is (3x)2 100 is 102 So (3x)2 - 102 Rule: Factor the difference of two square as the product of the sum and difference of the those terms. Thus: (3x – 10)(3x+ 10)
Caution • Be sure that you factor the common factor before factoring
Try • 4x2 – 9 • 2x3 – 8x
Repeated Factorization • Try: 81x4 – 16 • Note: After you factor, look at the factors.
Factoring Perfect Square Trinomials • Two ways • Area Model • Rule
Check for a Perfect Square Trinomial • Middle (linear) term is twice the product of the outside terms that are being squared. • Example: 4x2 + 12xy + 9y2 • leading term: (2x)2 • Last term: (3y)2 • Multiply the expression being square and multiply by 2 • 2(2x)(3y) which is the middle term.
Factor: 4x2 + 12xy + 9y2 • Since it is a perfect square trinomial • (2x)2 + 2(2x)(3y) + (3y)2 • Factor: Take the terms being squared in order and write as a binomial with the first sign and square the binomial. • (2x + 3y)2
Factor: 4x2 + 12xy + 9y2 • Set up for the area model • Sum is 12, product is (4)(9) • Numbers are 6xy and 6xy
Sum or Difference of Two Cube • Observe: • (A + B)3 = (A + B)(A2 - AB + B2) • (A - B)3 = (A - B)(A2 + AB + B2) • Words: Write the binomial, then square the first, change the signs, multiply together and square the second.
Factor: x3 + 125 • Rewrite as the sum of cubes • (x)3 + (5)3
Try • 25x4 – 25y6 • 2x3y – 18xy • 25y2 – 10y + 1 • 27x3 - 8
Summary • Binomial • Difference of two squares • Sum or Difference of two cubes • Trinomial • Area model • Grouping • Perfect square trinomial