1. you defined the variable intersectionx(end+1) and intersection(i) as array.
will give you also many points as long as the lenght of your array.
2. That is a numerical itteration what you do. In other words you will never reach your destination, you will only comming closer and closer.
from 1 to 0 as an example:
1; 0.5; 0.25; 0.125; ...
3. check if some answer exit in the range of dx=-5:0.000001:5; you can draw your function to see if you have an intersect. In case of existing intersect you have to check the convergency of your function in the range of searching.