Answer:
Step-by-step explanation:
Many ways to do this in the details.
All start by writing three equations with three unknowns
<em>-56 = a(3²) + b(3) + c</em>
-56 = 9a + 3b + c 1)
<em>-16 = a(-1²) + b(-1) + c</em>
-16 = a - b + c 2)
<em>-51 = a(-2²) + b(-2) + c </em>
-51 = 4a - 2b + c 3)
subtract equation 2 from equation 1
-40 = 8a + 4b
--10 = 2a + b
b = -10 - 2a 4)
subtract equation 3 from equation 1
-5 = 5a + 5b
-1 = a + b 5)
substitute 4 into 5
-1 = a + (-10 - 2a)
-1 = - a - 10
a = - 9
substitute a into 4
b = -10 - 2(-9)
b = 8
substitute a and b into any of 1, 2, or 3
-51 = 4(-9) - 2(8) + c
-51 = -36 - 16 + c
c = 1
y = -9x² + 8x + 1
We can use a plotting calculator to confirm our result.
