A drawn line of best fit already gives you the model, so use two points on the line rather than two scattered data dots. Read its value at , then find its slope by dividing the change in by the change in ; Desmos can handle that arithmetic. Match both numbers to . Watch the axis scale: a grid box may represent more than one input unit.
Hints
- Hint 1
A line of best fit follows the overall pattern but needn't pass through every measured dot. Use the labeled points on the line. What are their coordinates when you read horizontally and vertically?
- Hint 2
The -intercept is the line's value when . The slope is the change in divided by the matching change in . Keep the two points in the same order in both differences.
Step-by-step
Read the fitted line's intercept and slope
Step 1Read the two points on the line
The labels mark points on the fitted line. Reading horizontally and vertically gives and . Use these points, not two measured dots that might sit off the line.
- Step 2
Find the intercept
The -intercept is the line's -value when . Point gives . 's isn't the intercept because it occurs at .
- Step 3
Find the slope using the axis values
The slope is the change in thickness divided by the change in thousands of miles. Type in Desmos; it shows . Use the axis values, not the number of grid boxes. The negative sign fits a line that falls as miles driven increases.
- Step 4
Write the equation of the fitted line
In slope-intercept form, . Put both values you found into it: . The line predicts millimeters of brake pad thickness at thousand miles and a decrease of millimeter per additional thousand miles. Choice A.