The axis of symmetry in factored form uses a formula. The formula is x= ( (r+s) /2). The x is the axis of symmetry. The axis of symmetry uses the r and the s from factored form. Factored form is y= a (x-r) (x-s).
An example of a question is: Find the axis of symmetry for y=(x-8)(x+2) You would first sub the x-intercepts into the formula x= (8-2)/2 x=6/2 x=3