Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 6 - Section 6.5 - Synthetic Division and the Remainder Theorem - Exercise Set - Page 453: 31

Answer

The remainder is $0$. $\left \{-5,\frac{1}{3},\frac{1}{2}\right\} $.

Work Step by Step

The given equation is $\Rightarrow 6x^3+25x^2-24x+5=0$. The solution is $c=-5$. Synthetic division. Write the coefficients of the dividend as shown below. $\begin{matrix} -5) &6&25&-24&5 & ​\end{matrix}$ 1. Bring down $6$. $\begin{matrix} -5) &6&25&-24&5 \\ & & \\ & --& \\ & 6& ​\end{matrix}$ 2. Multiply $-5(6)=-30$. $\begin{matrix} -5) &6&25&-24&5 \\ & &-30&& \\ & --&--& \\ & 6& ​\end{matrix}$ 3. Add columns $\begin{matrix} -5) &6&25&-24&5 \\ & &-30&& \\ & --&--& \\ & 6&-5& ​\end{matrix}$ 4. Multiply $-5(-5)=25$. $\begin{matrix} -5) &6&25&-24&5 \\ & &-30&25& \\ & --&--&--& \\ & 6&-5&& ​\end{matrix}$ 5. Add columns $\begin{matrix} -5) &6&25&-24&5 \\ & &-30&25& \\ & --&--&--& \\ & 6&-5&1& ​\end{matrix}$ 6. Multiply $-5(1)=-5$. $\begin{matrix} -5) &6&25&-24&5 \\ & &-30&25&-5 \\ & --&--&--& --\\ & 6&-5&1& ​\end{matrix}$ 7. Add columns $\begin{matrix} -5) &6&25&-24&5 \\ & &-30&25&-5 \\ & --&--&--& --\\ & 6&-5&1&0 ​\end{matrix}$ Use $6,-5,1,0$ to write the quotient and remainder. The degree of the first term of the quotient is one less than the degree of the first term of the dividend. The quotient is $6x^2-5x+1$ and the remainder is $0$. The factor is $x-(c)=x-(-5)=x+5$. We can write the given equation as $\Rightarrow (x+5)(6x^2-5x+1)=0$. Now factor $6x^2-5x+1$ $\Rightarrow 6x^2-5x+1$ Rewrite the middle term $-5x$ as $-3x-2x$. $\Rightarrow 6x^2-3x-2x+1$ Group terms. $\Rightarrow (6x^2-3x)+(-2x+1)$ Factor each group. $\Rightarrow 3x(2x-1)-1(2x-1)$ Factor out $(2x-1)$. $\Rightarrow (2x-1)(3x-1)$ Back substitute. $\Rightarrow (x+5)(2x-1)(3x-1)=0$. Set each factor equal to zero. $x+5=0$ or $2x-1=0$ or $3x-1=0$ Isolate. $x=-5$ or $x=\frac{1}{2}$ or $x=\frac{1}{3}$ The solution set is $\{-5,\frac{1}{3},\frac{1}{2}\}$.
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