Answer:
a = 1.
Step-by-step explanation:
For the general vertex form:
y = a(x - b)^2 + c the line of symmetry is x = b.
y = ax^2 -2x - 3
y = a( x^2 - 2x/a) - 3
y = a[(x - 1/a)^2 - (1/a)^2] - 3
y = a(x - 1/a)^2 - 1/a - 3
Here the line of symmetry is x = 1 so we have:
1/a = 1
a = 1.
