Răspuns:
Explicație pas cu pas:
2^4n+2 = 2^2(2n+1) = (2^2n+1)^2 patrat perfect
____________
9^n+1 = (3^2)^n+1 = (3^n+1)^2 = patrat perfect
_____________
7^6n = (7^3n)^2 = patrat perfect
____________
15^n^2+n = 15^numar par = patrat perfect
n*2 + n = n(n+1) = produs de doua numere consecutive, deci numar par
