Answer:
y = -1.2x² +6.6x +2
Step-by-step explanation:
The quadratic regression function of a calculator or spreadsheet can do this for you. The resulting function is ...
y = -1.2x² +6.6x +2
_____
If you want to do this by hand, put the given (x, y) values into the formula ...
ax² +bx +c = y
and solve the resulting system of equations.
The third point tells you c=2, so you can simplify the system of equations to ...
a(-2)² +b(-2) +2 = -16 ⇒ 4a -2b = -18 ⇒ 2a -b = -9
a(3)² +b(3) +2 = 11 ⇒ 9a +3b = 9 ⇒ 3a +b = 3
Adding these equations together gives ...
(2a -b) +(3a +b) = (-9) +(3)
5a = -6 . . . . . . . . simplify
a = -1.2 . . . . . . . divide by 5
b = 3 -3a = 3 -3(-1.2) = 6.6 . . . . from the second equation
Now we know the coefficients are a=-1.2, b=6.6, c=2, so the function is ...
y = -1.2x² +6.6x +2
