Expert: Sherman D. - 1/14/2005

Question
Can you help me with this problem....

   y = (x+1)squared -9

Give the extrema and tell what kind?

When does the function increase?
When does the function decrease?
When is the function positive?

Answer
y = (x + 1)^2 - 9
y = ((x + 1)(x + 1)) - 9
y = (x^2 + 2x + 1) - 9
x^2 + 2x - 8

To find the "x" value of the Vertex, use this formula.
x = -b/(2a)
x = -2/2
x = -1

Now to find the "y" value of the Vertex, plug in the "x" value that you got above.
y = (-1)^2 + 2(-1) - 8
y = 1 - 2 - 8
y = -1 - 8
y = -1 + (-8)
y = -9

Vertex = (-1,-9)

When does the function increase?
x > -1

When does the function decrease?
x < -1

When is the function positive?
x^2 + 2x - 8
(x + 4)(x - 2)
"y" value is positive when x < -4 and x > 2

For a graph, go to www.calculator.com, click Graphing.