What is a major use of completing the square?

Completing the square is a technique that converts a quadratic polynomial of the form:y=ax^2+bx+c into:y=a(x-d)^2+eThis converted form can be used to identify the location of the turning point. The turning point is at:x=d and y=eFor a concave quadratic polynomial, the turning point occurs at the maximum value of the polynomial. For a convex quadratic polynomial, the turning point occurs at the minimum value of the polynomial.