Question

demonstrează ca (3 +6+9+...+147)+1225 e patrat perfect

Answer 1

$3 + 6 + 9 + ... + 147 + 1225$

$3(1 + 2 + 3 + ... + 49) + 1225$

$= 3 \times \frac{49(49 + 1)}{2} + 1225$

$= 3 \times \frac{49 \times 50}{2} + 1225$

$= 3 \times 49 \times 25 + 1225$

$= 147 \times 25 + 1225$

$= 3675 + 1225$

$= 4900$

$= 70 \times 70 = {70}^{2} = > p.p$