Algebra 2 Common Core

Published by Prentice Hall
ISBN 10: 0133186024
ISBN 13: 978-0-13318-602-4

Chapter 5 - Polynomials and Polynomial Functions - 5-3 Solving Polynomial Equations - Practice and Problem-Solving Exercises - Page 301: 39

Answer

The solutions are $x = 0, 5 - 2\sqrt {3}, \text{ and } 5 + 2\sqrt {3}$.

Work Step by Step

Rewrite this equation so all the terms are on the left side of the equation and that the equation equals $0$. $x^3 - 10x^2 + 13x = 0$ Factor out $x$ from each term: $x(x^2 - 10x + 13) = 0$ Use the Zero-Product Property by equating each factor to $0$, then solve each equation. First factor: $x = 0$ Second factor: $x^2 - 10x + 13 = 0$ We cannot factor this polynomial, so we resort to using the quadratic formula, which is: $x = \dfrac{-b \pm \sqrt {b^2 - 4ac}}{2a}$ where $a=1, b=-10,$ and $c=13$ is the constant. Let us plug in the numbers into the formula: $x = \dfrac{-(-10) \pm \sqrt {(-10)^2 - 4(1)(13)}}{2(1)}$ $x = \dfrac{10 \pm \sqrt {100 - 52}}{2}$ $x = \dfrac{10 \pm \sqrt {48}}{2}$ The number $48$ can be expanded into the factors $16$ and $3$: $x = \dfrac{10 \pm \sqrt {3(16)}}{2}$ $x = \dfrac{10 \pm 4\sqrt {3}}{2}$ $x = 5 \pm 2\sqrt {3}$ The solutions are $x = 0, 5 \pm 2\sqrt {3}$.
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