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Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley The Fundamental Theorem of Algebra ♦ Perform arithmetic operations on complex numbers ♦ Solve quadratic equations having complex solutions ♦ Apply the fundamental theorem of algebra ♦ Factor polynomials having complex zeros ♦ Solve polynomial equations having complex solutions 4.4

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Slide 4- 2 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Complex Numbers A complex number can be written in standard form as a + bi, where a and b are real numbers. The real part is a and the imaginary part is b.

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Slide 4- 3 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Example Write each expression in standard form. Support your results using a calculator. a) ( 4 + 2i) + (6 3i)b) ( 9i) (4 7i) c) ( 2 + 5i) 2 d) Solution

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Slide 4- 4 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Solution continued

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Slide 4- 5 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Quadratic Equations with Complex Solutions We can use the quadratic formula to solve quadratic equations if the discriminant is negative. There are no real solutions, and the graph does not intersect the x-axis. The solutions can be expressed as imaginary numbers.

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Slide 4- 6 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Example Solve the quadratic equation 4x 2 – 12x = –11. Solution

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Slide 4- 7 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Fundamental Theorem of Algebra The polynomial f(x) of degree n 1 has at least one complex zero. Number of Zeros Theorem A polynomial of degree n has at most n distinct zeros.

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Slide 4- 8 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Example Represent a polynomial of degree 4 with leading coefficient 3 and zeros of 2, 4, i and i in complete factored form and expanded form. Solution

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Slide 4- 9 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Conjugate Zeros Theorem If a polynomial f(x) has only real coefficients and if a + bi is a zero of f(x), then the conjugate a bi is also a zero of f(x).

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Slide 4- 10 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Example Find the zeros of f(x) = x 4 + 5x 2 + 4 given one zero is i. Solution

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Slide 4- 11 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Solution continued

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Slide 4- 12 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Example Solve x 3 = 2x 2 5x + 10. Solution

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Slide 4- 13 Copyright © 2006 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Solution continued

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