The point A is shown on the unit grid below.

Answer:
Coordinates of point B are (3, 5) and (5, 3).
Step-by-step explanation:
Coordinates of point A → (1, 1)
Let the coordinates of point B are (x', y')
Formula for the distance between points (x, y) and (x', y') is,
d = [tex]\sqrt{(x-x')^+(y-y')^2}[/tex]
AB = [tex]\sqrt{(x-1)^+(y-1)^2}[/tex]
[tex]2\sqrt{5}=\sqrt{(x-1)^2+(y-1)^2}[/tex]
[tex](2\sqrt{5})^2=(x-1)^2+(y-1)^2[/tex]
20 = (x - 1)² + (y - 1)²
Since point A lies on the intersection of two grid lines in the 1st quadrant, x and y must be the positive whole number.
For x = 0,
20 = (0 - 1)² + (y - 1)²
(y - 1)² = 20 - 1
y = 1 + √19
But y can't be a decimal, therefore, x = 0 is not the answer.
For x = 1
20 = (1 - 1)² + (y - 1)²
20 - 1 = (y - 1)²
y = 1 + √19
Not a whole number, so can't be the solution.
For x = 2,
20 = (2 - 1)² + (y - 1)²
y = 1 + √19
Not a whole number, therefore, not the answer.
For x = 3,
20 = (3 - 1)² + (y - 1)²
20 - 4 = (y - 1)²
y = 1 + √16
y = 5
Therefore, (3, 5) are coordinates of the point B.
For x = 4,
20 = (4 - 1)² + (y - 1)²
20 = 9 + (y - 1)²
y = 1 + √11
For x = 5,
20 = (5 - 1)² + (y - 1)²
20 - 16 = (y - 1)²
4 = (y - 1)²
y = 3
Therefore, (5, 3) the coordinates of point B.
The coordinates of [tex]B, (x,y)=(3,5)\text{ or }(5,3)[/tex]
From the diagram, the coordinates of [tex]A[/tex] are [tex](1,1)[/tex]
the distance from [tex]A[/tex] to [tex]B[/tex] is [tex]2\sqrt{5}[/tex]
Since [tex]B(x, y)[/tex] also lies on the grid, [tex]x[/tex] and [tex]y[/tex] should be integers and should satisfy the distance relationship
[tex](x-1)^2+(y-1)^2=(2\sqrt{5})^2\implies (x-1)^2+(y-1)^2=20[/tex]
There is a way to get [tex]\sqrt{5}[/tex] from Pythagoras rule
[tex]1^2+2^2=(\sqrt{5})^2\\\\\implies2^2+4^2=(2\sqrt{5})^2[/tex]
Which means we can either say
[tex]x-1=2 \text{ and } y-1=4\\\implies x=3 \text{ and } y=5\\\\\text{OR}\\\\x-1=4 \text{ and } y-1=2\\\implies x=5 \text{ and } y=3[/tex]
Therefore B is either at location [tex](3,5)[/tex] or [tex](5,3)[/tex]
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