help plz

The axis of symmetry is y = 3.

The axis of symmetry is equal to the average of the roots. When we factor $x^2-2x-3$, we get $(x+1)(x-3)$, so the roots are -1 and 3 as shown in the graph. $\frac{-1+3}{2} = 1$, so the axis of symmetry is $x=1$. 

Hope this helped