Can you please help me write a quadratic function 
with this set of data? 
(0,254)(4,234)(8,235)(12,239)(16,255) 

f(0) = 254
f(4) = 234
f(8) = 235
f(12) = 239

There is a terribly long formula for finding the 
quadratic regression formula.  When you plug 
into it you get:

y = f(x) = 75/224x� - 1451/280x + 1769/7 

Are you allowed to use a TI-83 or TI-84?  If so, then

press STAT then ENTER, 
enter the five x values under L1 and the five values for f(x) in L2.

press STAT then the right arrow then 5, then ENTER

You see:

y = ax�+bx+c
a=.3348214286
b=-5.182142857
c = 252.7142657
R�=.9564574654

Since R� is near 1, the fit is good.

plug those values into 

y = ax�+bx+c

y = f(x) = .3348214286x� - 5.182142857x + 252.7142857

Here's the graph of that, the o's are your 5 points above:





Edwin