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x = 2ⁿ × 3ⁿ⁺¹ + 6ⁿ × 5 + 2ⁿ⁺¹ × 3ⁿ⁺¹
x = 2ⁿ × 3ⁿ × 3 + 6ⁿ × 5 + 2ⁿ⁺¹ × 3ⁿ⁺¹
x = (2 × 3)ⁿ × 3 + 6ⁿ × 5 + (2 × 3)ⁿ⁺¹
x = 6ⁿ × 3 + 6ⁿ × 5 + 6ⁿ⁺¹
x = 6ⁿ × 3 + 6ⁿ × 5 + 6ⁿ × 6
x = 6ⁿ ( 3 + 5 + 6 )
x = 6ⁿ × 14 , unde 14 = 2 × 7
x = 6ⁿ × 2 × 7 ⇒ x divizibil cu 7
