# What is the vertex form of y= x^2-6x-21 ?

$y = {\left(x - 3\right)}^{2} - 30$
$x = - \frac{b}{2 a} = \frac{6}{2} = 3$
$y \left(3\right) = 9 - 18 - 21 = - 30$
Vertex form: $y = {\left(x - 3\right)}^{2} - 30$