If a quadratic function has zero at x=-9, then point (-9,0) lies on the graph of quadratic function.
A line of symmetry has equation x=-3.5 that is x+3.5=0.
Use formula for the distance from point
to the line AX+By+C=0:

Thus,

Answer: the distance is 5.5 units.
I hope this helps you
f (1+1)= f (1)+8
f (2)= 27+8
f (2)=35
f (2+1)= f (2)+8
f (3)= 35+8
f (3)=43
The slope intercept form is 1/2