a) The linear function for the 2005 estimate is given as follows: y = 30 + 5x.
b) The linear function for the 1990 estimate is given as follows: y = 53.75 + 2.25x.
c) They would be predicted to have the same cost in the year of 2013.
d) The 1990 prediction was closer, however it still had a large residual, hence neither was good enough.
The linear functions are defined in the slope-intercept format, given as follows:
y = mx + b.
In which:
Taking 2005 as the estimate, the function is given as follows:
y = 30 + 5x.
Taking 1990 as the estimate, the equation would be of:
y = 20 + 2.25x.
The estimate for 2005 would be of:
y = 20 + 2.25(15) = 53.75.
Hence the equation taking 2005 as the estimate would be of:
y = 53.75 + 2.25x.
The costs would be the same when:
30 + 5x = 53.75 + 2.25x.
2.75x = 23.75
x = 23.75/2.75
x = 8.63 -> + 2005 -> year of 2013.
The estimates for 2011(6 years after 2005) are given as follows:
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