Chapter 1.3, Problem 4E

To determine

To write : An equation of a line and interpret the slope.

Answer to Problem 4E

Equation of line is $y=\frac{1}{30}x+12$ .

Explanation of Solution

Given Information: - Given a linear graph.

Calculation:

As the line is passing through the points (0,12) and (90,9).

Therefore slope $=\frac{y_2-y_1}{x_2-x_1}$

  $\begin{array}{l}=\frac{9-12}{90-0}\\ =\frac{-3}{90}=\frac{-1}{30}\end{array}$

Now equation of line using point slope from

  $\begin{array}{l}y-y_1=m(x-x_1)\\ y-12=\frac{-1}{30}(x-0)\\ y-12=\frac{-1}{30}x\\ y=\frac{-1}{30}x+12\end{array}$

Here slope shows that for each mile there is $\frac{1}{30}$ gallons less in gasoline tank.