From 1970 to 1990, the average cost C of a
new car (in dollars) can be approximated by
the model
C = 34.3t^2+4086
where t is the year, with t = 0 corresponding
to 1970.
During which year was the average cost of
a new car $10000?

Question

From 1970 to 1990, the average cost C of a
new car (in dollars) can be approximated by
the model
C = 34.3t^2+4086
where t is the year, with t = 0 corresponding
to 1970.
During which year was the average cost of
a new car $10000?

campbell_st · Answer

let C = 10000

so 10000 = 34.3t^2 + 4086

subtract 4086 from booth sides

5914 = 34.3t^2

t^2 = 5914/34.3

$$t = \pm \sqrt{5914/34.3}$$

campbell_st · Answer

you'll need to evaluate for t then add it to 1970 to find the year

anonymous · Answer

so the answer would be.....

campbell_st · Answer

only consider the positive t value

campbell_st · Answer

its written above ... just pick up the calculator to evaluate t... then add it to 1970