College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 3, Polynomial and Rational Functions - Section 3.4 - Real Zeros of Polynomials - 3.4 Exercises - Page 320: 44

Answer

The rational zeros are $x=-3$ or $x=\frac{1}{2}$ or $x=2$. The polynomial in factored form is $(2 x - 1) (x - 2)^2 (x + 3) (x^2 + 1)$.

Work Step by Step

Alternate form: $2 x^6 - 3 x^5 - 13 x^4 + 29 x^3 - 27 x^2 + 32 x - 12 = (x - 2)^2 (2 x^4 + 5 x^3 - x^2 + 5 x - 3)$ Solve for x over the real numbers: $(x - 2)^2 (2 x^4 + 5 x^3 - x^2 + 5 x - 3) = 0$ Split into two equations: $(x - 2)^2 = 0$ or $2 x^4 + 5 x^3 - x^2 + 5 x - 3 = 0$ Take the square root of both sides: $x - 2 = 0$ or $2 x^4 + 5 x^3 - x^2 + 5 x - 3 = 0$ Add 2 to both sides: $x = 2$ or $2 x^4 + 5 x^3 - x^2 + 5 x - 3 = 0$ The left hand side factors into a product with three terms: $x = 2$ or $(2 x - 1) (x^2 + 1) (x + 3) = 0$ Split into three equations: $x = 2$ or $x + 3 = 0$ or $2 x - 1 = 0$ or $x^2 + 1 = 0$ Subtract 3 from both sides: $x = 2$ or $x = -3$ or $2 x - 1 = 0$ or $x^2 + 1 = 0$ Add 1 to both sides: $x = 2$ or $x = -3$ or $2 x = 1$ or $x^2 + 1 = 0$ Divide both sides by 2: $x = 2$ or $x = -3$ or $x = 1/2$ or $x^2 + 1 = 0$ Subtract 1 from both sides: $x = 2$ or $x = -3$ or $x = 1/2$ or $x^2 = -1$ $x^2 = -1$ has no solution since for all $x$ on the real line, $x^2 \geq 0$ and $-1<0$: Answer: The rational zeros are $x=-3$ or $x=\frac{1}{2}$ or $x=2$. The polynomial in factored form is $(2 x - 1) (x - 2)^2 (x + 3) (x^2 + 1)$.
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