Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Appendix C - Solving Polynomial Equations - Exercise Set C - Page A33: 5

Answer

$p(0) = -4$ $p(1) = -3$ $p(-3) = 101$ $p(7) = 5001$

Work Step by Step

We are given the polynomial $p(x) = 2x^4 + x^3 - 3x^2 + x - 4$ and asked to find $p(0), p(1), p(-3),$ and $p(7)$ using synthetic division and the Remainder Theorem. We can directly evaluate the polynomial at each point. Find $p(0)$: We divide $p(x)$ by $x$: \[ \begin{array}{r|rrrr} & 2 & 1 & -3 &1 &-4 \\ \hline 0 & & 0 & 0 & 0 & 0 \\ \hline & 2 & 1 & -3 & -1 & -4\\ \end{array} \] The rest is $-4$, so $p(0)=-4$. Find $p(1)$: We divide $p(x)$ by $x-1$: \[ \begin{array}{r|rrrr} & 2 & 1 & -3 &1 &-4 \\ \hline 1 & & 2 & 3 & 0 & 1 \\ \hline & 2 & 3 & 0 & 1 & -3\\ \end{array} \] The rest is $-3$, so $p(1)=-3$. Find $p(-3)$: We divide $p(x)$ by $x+3$: \[ \begin{array}{r|rrrr} & 2 & 1 & -3 &1 &-4 \\ \hline -3 & & -6 & 15 & -36 & 105 \\ \hline & 2 & -5 & 12 & -35 & 101\\ \end{array} \] The rest is $101$, so $p(-3)=101$. Find $p(7)$: We divide $p(x)$ by $x-7$: \[ \begin{array}{r|rrrr} & 2 & 1 & -3 &1 &-4 \\ \hline 7 & & 14 & 105 & 714 & 5005 \\ \hline & 2 & 15 & 102 & 715 & 5001\\ \end{array} \] The rest is $5001$, so $p(7)=5001$.
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