Conjugate Pairs Let f (x) is a polynomial function that has real coefficients. If a + bi, where b ≠ 0, is a zero of the function, the conjugate a – bi is also a zero of the function. Ex 1: Find a fourth degree polynomial with real coefficients that has -1, -1, and 3i as zeros.
Prime/Irreducible Factors Every polynomial of degree n > 0 with real coefficients can be written as the product of linear and quadratic factors with real coefficients, where the quadratic factors have no real zeros. A quadratic factor with no real zeros is said to be prime or irreducible over the reals.
Ex 2: Write the polynomial f (x) = x4 – x2 – 20 a. As the product of factors irreducible over the rationals. b. As a product of linear factors. c. As the product of linear factors and quadratic factors that are irreducible over the reals.
Ex 3: Find all the zeros of f (x) = x4 – 3x3 + 6x2 + 2x – 60 given that 1 + 3i is a zero of f .
Practice Assignment: Section 2.5B (pg 141) #35 – 52