[tex]3 + 6 + 9 + ... + 147 + 1225[/tex]
[tex]3(1 + 2 + 3 + ... + 49) + 1225[/tex]
[tex] = 3 \times \frac{49(49 + 1)}{2} + 1225[/tex]
[tex] = 3 \times \frac{49 \times 50}{2} + 1225[/tex]
[tex] = 3 \times 49 \times 25 + 1225[/tex]
[tex] = 147 \times 25 + 1225[/tex]
[tex] = 3675 + 1225[/tex]
[tex] = 4900[/tex]
[tex] = 70 \times 70 = {70}^{2} = > p.p[/tex]