Question

1+3+5+7....+19 ajutatima Carey stie

Answer 1

1+3+5+7+........+19
e o regula:(primul nr+al doilea nr) ori nr. de nr. totul :2
(1+19) ori 10  =20 x 10:2=200:2=100
       2
sper ca e bn nr. de nr. Verifica pls.

Answer 2

Aflam numarul de termeni:
$n= \frac{19 - 1}{2} + 1 = \frac{18}{2} + 1=9+1=10 \; termeni \\ \\ \text{Calculam suma } \\ \\ S = \frac{10(19+1)}{2}= \frac{10* 20}{2} = 10*10 = 10^{2} \\ cctd$