Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 1 - Section 1.4 - Linear Functions and Slope - Exercise Set - Page 216: 114

Answer

The coefficient of $x$ is $1$ and the coefficient of $y$ is $-2$.

Work Step by Step

Let the coefficient of $x$ be $A$ and $y$ be $B$. Now the equation can be written as, $Ax+By-12=0$ (I) To calculate the $y\ \text{intercept}$, substitute $x=0$ in equation (I); that is, $\begin{align} & A\times 0+By-12=0 \\ & By-12=0 \\ & By=12 \\ & y=\frac{12}{B} \end{align}$ It is given that the $y\ \text{intercept}=-6$. $\begin{align} & -6=\frac{12}{B} \\ & B=\frac{12}{-6} \\ & =-2 \end{align}$ Now, we will rewrite the equation in the slope intercept form $y=mx+c$. $\begin{align} & By=-Ax+12 \\ & y=\frac{-A}{B}x+\frac{12}{B} \end{align}$ This means that the slope is $\frac{-A}{B}$. It is given that the $\text{slope}=\frac{1}{2}$. Substituting the value of B $\begin{align} & \frac{-A}{-2}=\frac{1}{2} \\ & \frac{-A}{-2}\left( 2 \right)=\frac{1}{2}\left( 2 \right) \\ & A=\frac{2}{2} \\ & A=1 \end{align}$ Hence, the coefficient of $x$ is 1 and the coefficient of $y$ is $-2$.
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