Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Chapter 1 - Linear Functions - 1.5 Finding Equations of Lines - 1.5 Exercises - Page 76: 40

Answer

$\color{blue}{y=\dfrac{7}{2}x-4}$

Work Step by Step

Recall: (1) The slope $m$ of a line passing through points $(x_1, y_1)$ and $(x_2, y_2)$ is given by the formula $$m=\dfrac{y_2-y_1}{x_2-x_1}$$ (2) The slope-intercept form of a line's equation is $y=mx+b$ where $m$=slope and $(0, b)$ is the $y$-intercept. The table shows that the line passes through the point $(0, -4)$. This means that $b=-4$. Hence, the tentative equation fo the line that contains the given points is: $$y=mx-4$$ The line also contains the point $(4, 10)$. Substitute the $x$ and $y$ values of this point into the tentative equation above to obtain: \begin{align*} y&=mx-4\\ 10&=m(4)-4\\ 10+4&=4m\\ 14&=4m\\ \frac{14}{4}&=m\\ \frac{7}{2}&=m \end{align*} Therefore, the equation of the line that contains the given points in the table is $\color{blue}{y=\frac{7}{2}x-4}$.
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