What are the vertex and x-intercepts of the graph of the function below?
y= x2 - 2x - 24
a. vertex: (1,-25); intercepts: x = -4,6
b. vertex: (1, 23); intercepts: x = 4, -6
c. vertex: (1, 23); intercepts: x = -4,6
d. vertex: (1,-25); intercepts: x = 4, -6