Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Appendix A - Review - A.3 Polynomials - A.3 Assess Your Understanding - Page A30: 101

Answer

$(x-1)^2(x^2+x+1)^2$

Work Step by Step

Since $x^6=(x^3)^2$, then we have: $x^6-2x^3+1=(x^3)^2-2x^3+1$ Letting $x^3=u$ yields $=u^2-2u+1$ The quadratic trinomial above has $a=1$$b=-2$, and $c=1$ Since $a=1$, look for factors of $c=1$ whose sum is $-2$. These factors are $-1$ and $-1$. Use the factors found above to rewrite the middle term. Rewrite $-2u$ as $-u-u$ to obtain: $u^2-2u+1=u^2-u-u+1$ Group the terms. $=(u^2-u)+(-u+1)$ Factor out the GCF in each group. $=u(u-1)-1(u-1)$ Factor out the GCF $(u-1)$. $=(u-1)(u-1)$ Back substitute $a=x^3$. $=(x^3-1)(x^3-1)$ $=(x^3-1)^2$ With $1^3=1$< then the expression above is equivalent to: $=(x^3-1^3)^2$ Use special formula $a^3-b^3=(a-b)(a^2+ab+b^2)$ with $a=x$ and $b=1$. $=[(x-1)(x^2+x(1)+1^2)]^2$ $=[(x-1)(x^2+x+1)]^2$ Use law of the exponents $(ab)^2=a^2b^2$. $=(x-1)^2(x^2+x+1)^2$ Hence, the completely factored form of the given expression is $(x-1)^2(x^2+x+1)^2$.
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