E gresit ultimul termen, trebuie sa fie 101.
a₁=1
r=10
[tex] a_{n} [/tex] = 101
n=11 termeni
Cum am aflat n?
[tex] a_{n} [/tex] = 101
a₁+ (n-1)·r = 101
1+ (n-1)·10 = 101
(n-1)·10 = 100
n-1=10
n=11
S=[tex] \frac{(a_{1}+a_{n})*n}{2} = \frac{(1+101)*11}{2} = \frac{102*11}{2} =51*11=561[/tex]
Imi votezi ca cel mai bun raspuns?