Linear Algebra: A Modern Introduction

Published by Cengage Learning
ISBN 10: 1285463242
ISBN 13: 978-1-28546-324-7

Chapter 2 - Systems of Linear Equations - 2.2 Direct Methods for Solving Linear Systems - Exercises 2.2 - Page 79: 11

Answer

Row Echelon Form: $$ \begin{bmatrix} 3 && 5 \\ 0 && -\frac{31}{3} \\ 0 && 0 \end{bmatrix}$$ Reduced Row echelon form: $$ \begin{bmatrix} 1 && 0 \\ 0 && 1 \\ 0 && 0 \end{bmatrix}$$

Work Step by Step

$$ \begin{bmatrix} 3 && 5 \\ 5 && -2 \\ 2 && 4 \end{bmatrix}$$ Subtract $\frac{5}{3}$ times row 1 from row 2 & Subtract $\frac{2}{3}$ times row 1 from row 3 $$\sim \begin{bmatrix} 3 && 5 \\ 0 && -\frac{31}{3} \\ 0 && \frac{2}{3} \end{bmatrix}$$ Add $\frac{2}{31}$ times row 2 to row 3 $$\sim \begin{bmatrix} 3 && 5 \\ 0 && -\frac{31}{3} \\ 0 && 0 \end{bmatrix}$$ Which is in row echelon form Divide row 1 by 3 $$\sim \begin{bmatrix} 1 && \frac{5}{3} \\ 0 && -\frac{31}{3} \\ 0 && 0 \end{bmatrix}$$ Multiply row 2 by -(3/31) $$\sim \begin{bmatrix} 1 && \frac{5}{3} \\ 0 && 1 \\ 0 && 0 \end{bmatrix}$$ Subtract $\frac{5}{3}$ times row 2 from row 1 $$\sim \begin{bmatrix} 1 && 0 \\ 0 && 1 \\ 0 && 0 \end{bmatrix}$$ Which is in reduced row echelon form.
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