(x,y)∈{(−2,4),(−2,6),(0,10),(4,−2),(4,12),(6,−2),(6,12),(10,0),(10,10),(12,4),(12,6)}.
An equivalent form of the given equation is
x2+y2⟺x2−10x+y2−10y⟺(x−5)2+(y−5)2=10x+10y=0=50
with x+y=0. We therefore have to solve the equation a2+b2=50 for integers a and b.
As max(a2,b2)≤50 we get max(∣a∣,∣b∣)≤7. Furthermore we obtain min(a2,b2)≤25 which yields min(∣a∣,∣b∣)≤5. Analyzing the individual cases, we obtain (a,b)∈{(±1,±7),(±7,±1),(±5,±5)} as the only possible solutions. If (a,b)∈{(±1,±7),(±7,±1)}, we get that x−5=±1 and y−5=±7 (or x and y swapped), which yields x∈{4,6} and y∈{−2,12} (or y∈{4,6} and x∈{−2,12}). The case (a,b)=(±5,±5) gives x−5=±5 and y−5=±5 which is equivalent to x∈{0,10} and y∈{0,10}. The pair (x,y)=(0,0) is the only one violating x+y=0. Therefore, we get the (eleven) different pairs listed in the answer.