f(x)=x^2+12x+26
Vertex form of f(x) = a(x-h)^2 +k
We change f(x) into vertex form using completing the square method

We take half of square of middle term
middle term is 12
Half of square of 12 is
then 6^2 = 36
Add and subtract 36 to complete the square


The vertex form
