4.4 Notes: Factoring Polynomials
Factoring using a GCF: We can start by trying to pull out a GCF. Remember, there WILL be more factoring to do after this! A) x3 – 4x2 – 5x B) 3y5 – 48y3 C) 5z4 + 30z3 45z2
Factoring sum or difference of cubes: Sum or difference of cubes has: Only two terms Two perfect cubes You need to use one of these two formulas to factor sum or difference of cubes…no other factoring method works! SUM: (a + b)(a2 – ab + b2) DIFFERENCE: (a – b)(a2 + ab + b2)
SUM: (a + b)(a2 – ab + b2) DIFFERENCE: (a – b)(a2 + ab + b2) 1) look for GCF 2) make in to perfect cubes to use the formulas above A) x3 – 125 B) 27x3 – 8 C) 64x3 + 1
Factor by Grouping: This method is part of the factoring of quadratics method that we have been using. A) z3 + 5z2 – 4z – 20 B) 3y3 + y2 + 9y + 3 C) x3 + 2x2 – 9x + 18
A divisor is a factor of a polynomial is the remainder is zero
Finally….. Show that x + 3 is a factor of f(x) = x4 + 3x3 – x – 3, then factor completely. Step 1: use synthetic division to determine if x+3 is a factor Step 2: factor the polynomial.
And…. Show that x – 2 is a factor of f(x) = x4 – 2x3 + x – 2 then factor completely.