point A is at (1,1)
point B is 2 sqrt( 5 ) units from A and lies on the intersection of two grids.
write the coordinates for both positions available for B .
Don't know a way to solve this algebraically...but...by "intersection of two grids" I think you mean "laatice points" [ points with integer coordinates ]
We can construct a a circle with a radius of sqrt (20) centered at (1, 1)
I found these two possibilities for B....[ and there may be more ] ....(-3, 3) and (5, -1)
See the graph here : https://www.desmos.com/calculator/weqndpih8n