Question 1104413
As an alternative, you CAN try to work backward from the 'vertex' form into the polynomial form.  


Assuming "a" is 1, then {{{y=(x-h)^2+k}}}, for vertex being (h,k).


{{{y=x^2-2hx+h^2+k}}}, by doing the multiplication and simplification.


This corresponds to {{{y=x^2+bx+c}}}.
You have {{{b=-2h}}} and {{{c=h^2+k}}}.

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These should also help you:

<a href="https://www.algebra.com/my/Completing-the-Square-Using-Pictures.lesson?content_action=show_dev">LESSON:  Meaning of Completing The Square</a>
https://www.algebra.com/my/Completing-the-Square-Using-Pictures.lesson?content_action=show_dev


<a href="https://www.algebra.com/my/Completing-the-Square-to-Solve-General-Quadratic-Equation.lesson?content_action=show_dev">LESSON: How to Complete The Square and Solve Quadratic Equation</a>
https://www.algebra.com/my/Completing-the-Square-to-Solve-General-Quadratic-Equation.lesson?content_action=show_dev