Determine and state the vertex of f(x) = x2– 2x – 8 using the method of completing

x²-2x-8

X²-2x=8

X²= -2x + (-1)² = 8 + (-1)²

X²= -2x + 1 = 8 + 1

X²= -2x + 1 = 9

(X-1)² = 9

√(x-1)² = √9

X-1 = ± 3

X= 1 + 3= 4

X= 1 - 3= -2

X= 4 or X= -2

Step-by-step explanation:

A) Water height, H(g) = 8g^2 + 3g -4 - [9g^2 -2g -5] = 8g^2 + 3g -4 -9g^2 + 2g +5 = -g^2 +5g +1

b) g = 1
H(g) = -(1)^2 + 5(1) + 1 = -1 + 5 + 1 = 5

g=2
H(g) = -(2)^2 + 5(2) + 1 = -4 + 10 + 1 = 7

g=3
H(g) = -(3)^2 + 5(3) + 1 = -9 +15 +1 = 5

c) Greatest height

Find the vertex of the parabole

The vertex is at the mid point between the two roots.

To find the roots you can use the quadratic equation

The result is g = 5/2 + [√29]/2 and g = 5/2 - [√29]/2

The middle poin is 5/2 = 2.5

Now find H(2.5) = -(2.5)^2 + 5(2.5) + 1 = 7.5 ≈ 7.3