Given that the line y = x + 1 and parabola y2 = ax intersect at two points a and B, if OA vector multiplies ob vector = A2-1, find the value of real number a

Given that the line y = x + 1 and parabola y2 = ax intersect at two points a and B, if OA vector multiplies ob vector = A2-1, find the value of real number a

a=2or-1