
Doug C. answered 11/10/23
Math Tutor with Reputation to make difficult concepts understandable
You will need to know how to complete the square to convert to vertex form.
y = (x2 + 2x + ___) + 5 [since the leading coefficient is 1, simply group the 1st two terms leaving a space to "complete the square", which converts the expression in parentheses to a perfect square trinomial]
To complete the square, take half of b and square it. Since b = 2, 1/2 (2) = 1 and 12=1. You are going to place a 1 in the placeholder so you need to subtract 1 to compensate:
y = (x2 + 2x + 1) + 5 - 1
y = (x2 + 2x + 1) + 4
Now rewrite the trinomial as a binomial squared.
y = (x + 1)2 + 4
In that form it is easy to identify the vertex as (-1, 4).
The following Desmos graph shows the parabola in both forms along with the vertex.
Rows 4 -12 generalize the process for converting from standard form to vertex form.
desmos.com/calculator/vfulna0ai9
Use the sliders on a,b,c to see the generalized parabola take on different forms.
Rows 13-17 show a more complicated example for converting from standard to vertex form.