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: 98

Answer

Calculate the intercepts of the graph and locate the points. Connect the two points by a straight line.

Work Step by Step

Consider the general form of a line’s equation $Ax+By+C=0$ Follow the steps given below to graph the equation using intercepts. Step 1: Calculate the $x$ intercept. Substitute $y=0$ in the given equation $Ax+By+C=0$ and find the value of $x$ $\begin{align} & Ax+B\times 0+C=0 \\ & Ax=-C \\ & x=-\frac{C}{A} \end{align}$ So, the line passes through the point $\left( -\frac{C}{A},0 \right)$. Step 2: Calculate the $y$ intercept. Substitute $x=0$ in the given equation $Ax+By+C=0$ and calculate the value of $y$ $\begin{align} & A\times 0+By+C=0 \\ & By=-C \\ & y=-\frac{C}{B} \end{align}$ So, the line passes through the point $\left( 0,-\frac{C}{B} \right)$. Step 3: Graph the equation of the line. Locate two intercepts $\left( -\frac{C}{A},0 \right)$ and $\left( 0,-\frac{C}{B} \right)$. Connect them by a straight line to graph the given equation $Ax+By+C=0$. Example: Consider the given linear equation $2x+3y+6=0$ Follow the steps given below to graph the equation using intercepts: Step 1: Calculate the $x$ intercept. Substitute $y=0$ in the given equation $2x+3y+6=0$ and find the value of $x$ $\begin{align} & 2x+3\times 0+6=0 \\ & 2x=-6 \\ & x=\frac{\left( -6 \right)}{2} \\ & =-3 \end{align}$ So, the $x$ intercept of the given equation $2x+3y+6=0$ is $-3$. Hence, the line passes through $\left( -3,0 \right)$. Step 2: Calculate the $y$ intercept. Substitute $x=0$ in the given equation $2x+3y+6=0$ and find the value of y $\begin{align} & 2\times 0+3y+6=0 \\ & 3y=-6 \\ & y=\frac{\left( -6 \right)}{3} \\ & =-2 \end{align}$ So, the $y$ intercept of the given equation $2x+3y+6=0$ is $-2$. Hence, the line passes through $\left( 0,-2 \right)$. Step 3: Graph the equation of the line. Locate the two intercepts $\left( -3,0 \right)$ and $\left( 0,-2 \right)$ in the graph. Connect them by a straight line. The graph of given equation $2x+3y+6=0$ is as follows:
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