Question

What is f(x)=3x^2-18x+23 into vertex form

Answer 1

$3x^2-18x+23=3(x^2-6x)+23=3(x^2-6x+9-9)+23$
$\quad=3((x-3)^2-9)+23=3(x-3)^2-27+23=3(x-3)^2-4$

The vertex is then $(3,-4)$.