Răspuns :
suma de 12 termeni
a = ( 1 + 23 ) · 12 / 2 = 24 · 12 :2 =12 ·12
a = 12²
√a = √12² = 12 ∈ N
a = ( 1 + 23 ) · 12 / 2 = 24 · 12 :2 =12 ·12
a = 12²
√a = √12² = 12 ∈ N