A)find the quadratic function that models data as a function of x, the number of weeks.
weeks- 0,1,2,3,4,5,6
#- 585,582,629,726,873,1070,1317
On your TI-83 or TI-84,
Press CLEAR
Press STAT
Press 1
Put in the values 0,1,2, thru 6, in L1
Put in the values 585,582, thru 1317, in L2
Press STAT
Press the right arrow key
Press 5
Press ENTER
You will read:
y=ax²+bx+c
a=25
b=-28
c=585
So quadratic equation (model) is
y = f(x) = 25x² - 28x + 585
B) use the model to estimate the number at 8 weeks
y = f(8) = 25(8)² - 28(8) + 585 = 1961
If you aren't allowed to use a calculator, post again,
stating so.
Edwin