We know that equation of a parabola is given by :-
y = a(x-h)² + k
Where (h,k) is the vertex of parabola and (x,y) is any point on its curve.
Given that vertex of parabola is (3,5) and one point (x,y) is (6,-1).
We can plug the given information in the equation of parabola and solve it for value of 'a' :-
-1 = a(6 - 3)² + 5
-1 = a(3)² + 5
-1 = 9a + 5
9a = -1 -5 = -6
a =
a = is the final answer.