Let’s use a specific quadratic equation as an example to demonstrate these steps. Start with this equation:
y = 2x2 + 8x +
After completing the square for the equation y = 2x2 + 8x + 6y, we have transformed it into the equivalent equation with the completed square term:
y = 2( x2 + 4x + 4 ) − 2
The term that was added and subtracted is 4, which is (b/2a)2. The vertex form of the equation, therefore, is:
y = 2( x + 2 )2 − 2
In this form:
So the vertex of the parabola described by this equation is at the point (−2,−2)