Question

What equation do I write?

Answer 1

`y=-(1)/(30)x+12`

Explanation:

`\boxed{\begin{minipage}{6.3 cm}\underline{Slope-intercept form of a linear equation}\\\\$y=mx+b$\\\\where:\\ \phantom{ww}$\bullet$ $m$ is the slope. \\ \phantom{ww}$\bullet$ $b$ is the $y$-intercept.\\\end{minipage}}`

The y-intercept is the y-value of the point at which the line crosses the y-axis.

Therefore, from inspection of the given graph, the y-intercept is 12:

• b = 12

The slope of a line is the change in y over the change in x.

From inspection of the given graph, the change in y is -3 and the change in x is 90. Therefore, the slope is:

• 
  `\sf m=(-3)/(90)=-(1)/(30)`

Substitute the found values of m and b into the slope-intercept formula to create an equation of the line:

• 
  `y=-(1)/(30)x+12`