Question 117315
The x distance from the vertex to the first x intercept is the same as the distance from the vertex to the second x intercept. 
A vertical line through the vertex is a line of symmetry. 
For example,
{{{y=(x-1)^2-1}}}
has a vertex at (1,-1)
The first x intercept is x=0, 1 unit away from the vertex.
The second x intercept is x=2, also 1 unit away from the vertex. 
{{{ graph( 300, 200, -5, 5, -5, 5, (x-1)^2-1) }}}