Suma Gauss 1+2+3+...+x=[x(x+1)]/2
4=2² si 8=2³
2²⁽ˣ²⁺ˣ⁾/² = 2³ˣ¹⁴
2²⁽ˣ²⁺ˣ⁾/² = 2⁴² bazele sun aceleasi, egalam puterile
2(x²+x)/2=42
x²+x=42
x²+x-42=0
a=1, b=1, c= - 42
Δ=b²-4ac=1²+168=169 > 0
x₁=( -1+13)/2=12/2=6 ∈ N
x₂=( -1-13)/2= -14/2= -7 ∉ N
Singura solutie convenabila este x = 6 ∈ N