Question

calcule a soma dos 100 primeiros termos da PA 1,3,5,7...

Answer 1

a100= a1+99·r
a100= 1+99·2
a100= 1+198
a100= 199

Sn= $\frac{(a1+an)×n}{2}$
S100= $\frac{(1+199) · 100}{ 2}$
S100= $\frac{200×100}{2}$
S100= $\frac{20000}{2}$
S100= 10000