Which equation represents a graph with a vertex at open paren 1 comma negative 6 close paren ?
A
y is equal to 3 x squared minus 3 x minus 6B
y is equal to 3 x squared minus 8 x minus 1C
y is equal to 3 x squared plus 6 x minus 3D
y is equal to 3 x squared minus 6 x minus 3