Chapter 3 3-4 factoring polynomials

Objectives Use the Factor Theorem to determine

factors of a polynomial.Factor the sum and difference of two

cubes.

Factor Theorem Recall that if a number is divided by any

of its factors, the remainder is 0. Likewise, if a polynomial is divided by any of its factors, the remainder is 0.

The Remainder Theorem states that if a polynomial is divided by (x – a), the remainder is the value of the function at a. So, if (x – a) is a factor of P(x), then P(a) = 0.

Factor theorem

Example#1 Determine whether the given

binomial is a factor of the polynomial P(x).

A. (x + 1); (x2 – 3x + 1) B. (x + 2);

(3x4 + 6x3 – 5x – 10)

Example#2 Determine whether the given

binomial is a factor of the polynomial P(x).

a. (x + 2); (4x2 – 2x + 5)

Student guided practice Do problems 1-3 in your book page 177

Factoring You are already familiar with methods

for factoring quadratic expressions. You can factor polynomials of higher degrees using many of the same methods you learned.

Factoring by Grouping

Factor: x3 – x2 – 25x + 25. Factor: 2x3 + x2 + 8x + 4.

Factoring polynomials Just as there is a special rule for

factoring the difference of two squares, there are special rules for factoring the sum or difference of two cubes.

Factoring the Sum or Difference of Two Cubes Factor the expression. 4x4 + 108x 125d3 – 8

Student guided practice Do problems 4-8 in your book page 176

Geometry Application

The volume of a plastic storage box is modeled by the function V(x) = x3 + 6x2 + 3x – 10. Identify the values of x for which V(x) = 0, then use the graph to factor V(x).

Geometry application The volume of a rectangular prism

is modeled by the function V(x) = x3 – 8x2 + 19x – 12, which is graphed below. Identify the values of x for which V(x) = 0, then use the graph to factor V(x).

Homework Do odd problems from 17-32 in your

book page 177

closure Today we learned about polynomials Next class we are going to learned

about finding real roots in polynomials