Răspuns:
1+4+7+...+97+100=
[tex] 3 \times \frac{n(n + 1)}{2}}
[tex]3 \times {100(100 + 1)}^{2} \\ 3 \times \frac{100 \times 101}{2} \\ 3 \times \frac{10100}{2} \\ 3 \times 5050 = 15150[/tex]
Sper ca te-am ajutat :)
