We are given the following quadratic equation

We are asked to convert this equation into the vertex form given by

Let us convert the given quadratic equation into the above form.

Now we have to add a number to both sides of the equation such that the terms inside the parenthesis become perfect squares.
How about 64?

Why did we add 128 on the left side?
Because 64 is being multiplied by 2 on the right side of the equation so 64x2 = 128

As you can see, the equation has been converted into the vertex form.
Finally, the x-coordinate of the minimum is
The value of h is the x-coordinate of the minimum and the value of k is the y-coordinate of the minimum
Comparing the above equation with the standard vertex form, we see that
h = 8
Therefore, 8 is x-coordinate of the minimum