Question

Aflati numarul perechilor ordonate de numere intregi (x,y) cu proprietatea x²+y²=5

Answer 1

x,y ∈ Z
x²+y²=5
=> x²,y² ∈ {1,4}
x²=1 => x₁=-1
    ↓        x₂= 1
y²=4 => y₁=-2
             y₂= 2

x²=4 => x₃=-2
   ↓        x₄=2
y²=1 => y₃=-1
             y₄=1
=> (x,y) ∈ {(-2,-1),(-2,1),(1,-2),(1,2)}