Answer:
(a) Figure 3
(b) 66.2 meters per second
Explanation:
You want to know the figure that shows the best fit of a curve to the data, and you want to know the value of the curve when x = 8 seconds.
Best fit
The fit is best when the difference between the data points and the curve is minimized. Often the sum of the squared differences is the metric that is minimized when the fit is best.
The gaps between the data points and the curve shown are greatest in Figures 1 and 2, so Figure 3 has the best fit.
Estimated value
The speed is estimated by the equation of the curve of best fit as ...
y = 0.6x² +2.1x +11
A slight rearrangement can make this easier to evaluate:
y = (0.6x +2.1)x +11
For x=8, the value of y is ...
y = (0.6·8 +2.1)·8 +11 = 6.9·8 +11 = 66.2
The predicted speed at 8 seconds is 66.2 meters per second.