Intermediate Algebra for College Students (7th Edition)

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

Chapter 3 - Section 3.5 - Determinants and Cramer’s Rule - Exercise Set - Page 241: 51

Answer

Yes.

Work Step by Step

The given coordinates are $\Rightarrow (x_1,y_1)=(3,-1)$ $\Rightarrow (x_2,y_2)=(0,-3)$ $\Rightarrow (x_3,y_3)=(12,5)$ The determinant to show the three points is $\Rightarrow \begin{vmatrix} x_1& y_1& 1\\ x_2& y_2& 1\\ x_3& y_3& 1 \end{vmatrix}$ Plug all the values. $\Rightarrow \begin{vmatrix} 3& -1& 1\\ 0& -3& 1\\ 12& 5& 1 \end{vmatrix}$ Perform $R_3\rightarrow R_3-4R_1$. $\Rightarrow \begin{vmatrix} 3& -1& 1\\ 0& -3& 1\\ 12-4(3)& 5-4(-1)& 1-4(1) \end{vmatrix}$ Simplify. $\Rightarrow \begin{vmatrix} 3& -1& 1\\ 0& -3& 1\\ 0& 9& -3 \end{vmatrix}$ Perform $R_3\rightarrow R_3+3R_2$. $\Rightarrow \begin{vmatrix} 3& -1& 1\\ 0& -3& 1\\ 0+3(0)& 9+3(-3)& -3+3(1) \end{vmatrix}$ Simplify. $\Rightarrow \begin{vmatrix} 3& -1& 1\\ 0& -3& 1\\ 0& 0& 0 \end{vmatrix}$ All elements below the diagonal are zero. Hence, the determinant is the multiplication of the main diagonal elements. $\Rightarrow 3\cdot (-3)\cdot (0) $ Simplify. $\Rightarrow 0 $ The determinant is zero. Hence, the points are colinear.
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