If the line of symmetry is x =2.....then this is the x coordinate of the vertex
We have the form
y = a(x - h)^2 + k where h is the x oordinate of the vertex ....we need to find a and k thusly
1 = a (1 - 2)^2 + k → 1 = a + k
-1 = a (5 - 2)^2 + k → -1 = 9a + k
Subtract the second equation from the first
2 = -8a
a = 2/-8 = -1/4
And 1 = -1/4 + k
k = 1 + 1/4 = 5/4
So we have that
y =(-1/4) ( x - 2)^2 + 5/4
y = (-1/4) ( x^2 -4x + 4) + 5/4
y = (-1/4)x^2 + x -1 + 5/4
y = (-1/4)x^2 + x + 1/4
a = -1/4 b = 1 c = 1/4
And their sum is 1