Question

Fie secventa de numere naturale 11,12,13,14,...,101
a) determina cate numere are secventa
b) calculeaza s= 11+12+13+...+101

Answer 1

a) 11,12,13,14,...,101
(101 - 11) + 1 = 90 + 1 = 91 (numere)

b) S = 11+12+13+...+101
S = (101 + 11) × 91 : 2
S = 112 ×91 : 2
S = 56 × 91
S = 5096

Answer 2

a)
t1=1+10
t2=2+10
..............
101-10=91=t91
Secventa are 91de termeni
b)
S=(1+2+..+101)-(1+2+...+10)
=101*102:2-10*11:2
=5151-55
=5096