CPM Homework Help : INT2 Problem 9-143

Complete the square for $y = x^2 + 8x$ to determine the vertex. Then determine the x-intercepts and make a sketch of the parabola.

Hint:

Completed square polynomials follow the form $y = x^2 + 2bx + b^2$ .
What value of $b$ will create $8x$ ?

Answer:

To complete the square, let $b = 4$ , so the completed square form would be $y = (x + 4)^2 -16$ .
Where will the vertex be? Where will the $x$ -intercepts be?