16 = 4² → patrat perfect
2⁶ = ( 2³ )² = 8² → patrat perfect
90 = 3² x 10 → nu este patrat perfect
3⁴ = ( 3² )² = 9² → patrat perfect
4 × ( 3² + 3³ ) = 2² x ( 9 + 27 ) = 2² x 36 = 2² x 6² = ( 2 x 6 )² = 12² → patrat perefct
2⁴ + 9 = 16 + 9 = 25 = 5² → patrat perfect
121 = 11² → patrat perfect