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: 113

Answer

The coefficient of $x$ is $-6$ and the coefficient of $y$ is $3$.

Work Step by Step

Let the coefficient of $x$ be $A$ and $y$ be $B$. The equation becomes $Ax+By-12=0$ (I) To calculate the $x\ \operatorname{intercept}$, substitute $y=0$ in the equation (I); that is, $\begin{align} & Ax+B\times 0-12=0 \\ & Ax-12=0 \\ & Ax=12 \\ & x=\frac{12}{A} \end{align}$ It is given that the $x\ \text{intercept}=-2$. $\begin{align} & -2=\frac{12}{A} \\ & -2A=12 \\ & A=\frac{12}{-2} \\ & =-6 \end{align}$ Now, 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 provided that the $y\ \text{intercept}=4$. $\begin{align} & 4=\frac{12}{B} \\ & B=\frac{12}{4} \\ & =3 \end{align}$ Hence, the coefficient of $x$ is $-$ 6 and the coefficient of $y$ is 3.
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