Quadratic function ( in standard form ):
y = a x² + b x + c
x = 0:
635 = 0 + 0 + c
c = 635
x = 1:
644 = a + b + 635
a + b = 9
x = 2:
719 = 4 a + 2 b + 635
4 a + 2 b = 84
and now we have a system:
a + b = 9 / * ( - 2 )
4 a + 2 b = 84
-------------------------
- 2 a + 2 b = - 18
+
4 a + 2 b = 84
-------------------------
2 a = 66
a = 33; b = - 24;
Function is:
f ( x ) = 33 x² - 24 x + 635
f ( 8 ) = 33 * 64 - 24 * 8 + 635 = 2,112 - 192 + 635 = 2,555
Answer: The number of waterfowl on week 8 would be 2,555.
