Odpowiedzi

2010-04-11T17:56:37+02:00

an = a1 + (n− 1)r

a₃ = a₁ + 2r
a₆ = a₁ +5r

4 = a₁ + 2r |*(-1)
19 = a₁ +5r
19 - 4 = 5r - 2r
15 = 3r |: 3
r = 5

a₁ = 4 - 2r
a₁ = 4 - 10
a₁ = -6

an = a₁ + (n - 1)r
an = -6 + (n - 1)5
an = -6 + 5n - 5
an = 5n -11

200 > 5n - 11
211 > 5n |:5
n < 42,2

 

(- ∞ ; 42,2 ) i n ∋ do N stąd: n={1,2,3, ...,42}