Answer:
The minimum y-value is
or

Explanation:
we have

This is the equation of a vertical parabola open up
The vertex is the minimum y-value on the graph
Convert the equation into vertex form
Group terms that contain the same variable, and move the constant to the opposite side of the equation

Factor the leading coefficient

Complete the square. Remember to balance the equation by adding the same constants to each side


Rewrite as perfect squares

------> equation in vertex form
The vertex is the point (-0.5,-7.75)
therefore
The minimum is the point (-0.5,-7.75)
The minimum y-value is

see the attached figure to better understand the problem