The graph of y = ax^2 + bx + c, in which a, b, and c are real numbers, is shown. What is the value of a + 2b - c? Express your answer in simplest radical form.
+128399 In vertex form we have
y = a ( x - h)^2 + k (h,k) is the vertex and (x,y) is a point on the graph
So
-8 = a( 0 - 1)^2 + (-9)
1 = a1^2
a = 1
So we have
y = ( x - 1)^2 - 9
y =x^2 - 2x + 1 - 9
y = x^2 - 2x - 8
b = -2 c = -8
a + 2b - c =
1 + (2)(-2) - (-8) =
1 - 4 + 8 =
5
