Monday, December 13, 2010

Identifying special situations in factoring

  • Difference of two squares
  • a2- b= (a + b)(a - b)
    • 3 examples
    • 32 - 22= (3+2)(3-2)
    • 42 - 1= (4+1)(4-1)
    • 22 - 1= (2+1)(2-1)
  • Trinomial perfect squares
    • a+ 2ab + b= (a + b)(a + b) or (a + b)2
      • 3 examples
      • 4x2 + (2)(4x)(1) + 12 = (4x+1)2
      • 3x2 + (2)(3x)(2) + 22 = (3x+2)2
      • X2 + (2)(X)(8) + 82 = (X+8)2
    • a2 - 2ab + b= (a - b)(a - b) or (a - b)2
      • 3 examples
      • 6x2 - 2(6x)(10) + 102 = (6x-10)2
      • 9x2 - 2(9x)(5) + 5 = (9x-5)2
      • 4x2 - 2(4x)(12y) + 12y = (4x-12y)2



  • Difference of two cubes



    • a3 - b3
      • 3 - cube root 'em
      • 2 - square 'em
      • 1 - multiply and change
        • 3 examples
        • x3 - 125 = (x-5)(x2 + 5x + 25)
        • x3 - 64= (x-4)(x2+4x+16)
        • x3 - 27= (x-3)(x2+3x+9)


  • Sum of two cubes



    • a3 + b3 
      • 3 - cube root 'em
      • 2 - square 'em
      • 1 - multiply and change
        • 3 examples
        • x3 + 8 = (x+2)(x2-2x+ 4)
        • x3 + 27= (x+3)(x2-3x +9)
        • x3 + 125 = (x+5)(x2-5x +25)


  • Binomial expansion
    • (a + b)3 = Use the pattern a3+3a2b+3ab2+b3
    • (a + b)4 = Use the pattern a^4+4a3b+6a2b2+4ab3+b^4












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