+1557 The parabola $y = ax^2 + bx + c$ is graphed below. Find $a + b + c$. (The grid lines are one unit apart.)
The parabola passes through (-3,7), (-1,5), and (2,8).
+37147 Much easier to answer this if we had the graph to which the post refers.... 
+129895 We can solve these equations
7 = a (-3)^2 + b(-3) + c
5 = a(-1)^2 + b(-1) + c
8 = a(2)^2 + b(2) + c
Simplify as
9a - 3b + c = 7 (1)
a - b + c = 5 (2)
4a + 2b + c = 8 (3)
Multiply (2) by -3 and add to (1)
6a - 2c = -8 → 3a - c = -4 (3)
Multiply (2) by 2 and add to (3)
6a + 3c = 18 → 2a + c = 6 (4)
Add (3) and (4)
5a = 2
a = 2/5
To find c
2(2/5) + c = 6
4/5 + c = 6
c = 6 -4/5 = 26/5
To find b
2/5 - b + 26/5 = 5
b = 2/5 + 26/5 - 25/5
b = 3/5
a + b + c =
2/5 + 3/5 + 26/5 =
31 / 5
