Question

Sa se calculeze sumele:
a) 6+10+14+...+362
b)1+5+5²+5³+....+5¹²​

Answer 1

a) suma unei progresii artimetice

numarul de elemente= (362-6)/4=356/4=89

$S_a=\frac{(6+362)*89}{2 }=16376$

6-primul termen

362-ultimul termen

89-numarul de elemente

b)suma unei progresii geometrice

q=5-ratia progresiei geometrice

$S_g=\frac{1(1-5^{13})}{1-5}$