College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 3 - Mid-Chapter Check Point - Page 390: 14

Answer

$x=1$ and $x=-2$

Work Step by Step

$x^{3} - 3x + 2 = 0$ Using the Rational Zero Theorem, we find the possible rational zeros as the ratio between the constant term and the leading coefficient: $$PossibleZeros: \frac{+}{}\frac{1}{1}, \frac{+}{}\frac{2}{1}$$ and we use long division using the first possible zero (+1, also expressed as $x-1$): ...............$x^{2} + x - 2$ ..............._______________ $(x - 1)|x^{3} + 0x^{2} - 3x + 2$ ..............$-x^{3} + x^{2}$ ...............________ ............................$x^{2} - 3x$ ............................-$x^{2} + x$ ..........................._________ ...................................$-2x + 2$ .......................................$2x - 2$ ....................................._________ ...............................................0 which means we can now re-write the original equation as: $$(x-1)(x^{2} + x -2) = 0$$ Since two factors of $2$ that, when substracted, give $1$ are $2$ and $1$, we can also re-write it as: $$(x-1)[(x+2)(x-1)]=0$$ $$(x-1)^{2}(x+2) = 0$$ Where $x-1=0$ and $x+2=0$, therefore $x=1$ and $x=-2$.
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