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 215: 97

Answer

Solve the equation for $y$, transforming it into the slope–intercept form $y=mx+b$. The coefficient of $x$ will be the slope of the line and the constant term will be the $y$ intercept.

Work Step by Step

Consider the general form of a line’s equation $Ax+By+C=0$ Follow the steps given below to calculate the slope and y intercept of the given general equation: Step 1: Find the value of $y$ by rearranging the terms of the equation $Ax+By+C=0$ Subtract $Ax+C$ from both sides of the above equation: $\begin{align} & Ax+By+C-Ax-C=0-Ax-C \\ & By=-Ax-C \end{align}$ Divide both sides by B $\begin{align} & \frac{By}{B}=\frac{-Ax-C}{B} \\ & y=-\frac{A}{B}x-\frac{C}{B} \end{align}$ Step 2: Then compare it to the slope intercept form of the line. The coefficient of $x$ will be the slope of the line and the constant term will be the $y$ intercept. So, the slope of the line is $m=-\frac{A}{B}$ and the $y$ intercept is $b=-\frac{C}{B}$. Example: Consider the following line’s equation $3x-4y-6=0$ Step 1: To find the value of $y$, rearrange the terms of the equation Subtract $3x-6$ from both sides of the equation $\begin{align} & 3x-4y-6=0 \\ & 3x-4y-6-\left( 3x-6 \right)=0-\left( 3x-6 \right) \\ & 3x-4y-6-3x+6=0-3x+6 \\ & -4y=-3x+6 \end{align}$ Divide both sides by $-4$ $\begin{align} & \frac{\left( -4y \right)}{\left( -4 \right)}=\frac{-3x+6}{\left( -4 \right)} \\ & y=\frac{3}{4}x-\frac{3}{2} \end{align}$ Step 2: Compare it to the slope-intercept form of the line. The coefficient of $x$ will be the slope of the line and the constant term will be the $y$ intercept. So, the slope of the line is $m=\frac{3}{4}$ and the $y$ intercept is $b=-\frac{3}{2}$.
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