Question 932055
Use Completing The Square to put the function into the standard form which you want.  Use the lessons,  


<a href="http://www.algebra.com/my/Completing-the-Square-Using-Pictures.lesson?content_action=show_dev">What does Completing The Square Mean?</a>
http://www.algebra.com/my/Completing-the-Square-Using-Pictures.lesson?content_action=show_dev  
and  
<a href="http://www.algebra.com/my/Completing-the-Square-to-Solve-General-Quadratic-Equation.lesson?content_action=show_dev">Using Completing the Square to Solve Quadratic Equation</a>
http://www.algebra.com/my/Completing-the-Square-to-Solve-General-Quadratic-Equation.lesson?content_action=show_dev


The factor "a" either stretches or shrinks the parabola vertically; and if a<0, forces the parabola to open downward and have a vertex as a maximum.  Your given function will be such a form.