Question

Identify the vertex, the axis of symmetry, the maximum or minimum value, and the range of the parabola.y= - x2 + 8x - 19The vertex is(4,-3)is this correct ?

Answer 1

Genaral equation of a parabola: y = ax^2 + bx + c

X of the vertex: x = -b/2a

In this case a = -1, b = 8 and c = -19

Therefore X for the vertex is x = -8/(2)(-1) = -8/-2 = 4

To find the Y of the vertex, we use the original equation an the value we just foud for X

y = -x^2 + 8x - 19

y = -(4)^2 + 8(4) - 19

y = -16 + 32 - 19

y = -3

So the vertex is (4, -3)