Odpowiedzi

2010-04-14T15:47:32+02:00
(an) - ciąg arytmetyczny.
a₅ = 19 = a₁ +4r
a₄ = 5a₁

5a₁ + r = a₁ + 4r
a₁ = ¾r

¾r + 4r = 19
r = 4

a₁ = ¾r = ¾*4 = 3

Odp. Pierwszy wyraz wynosi 3, natomiast różnica ciagu - 4.
2 5 2
2010-04-14T15:50:29+02:00
A₅ = 19
a₄ = 5a₁

a₁ + 4r = 19
a₁ + 3r = 5a₁ >>>>> 4a₁ = 3r /:4 >>> a₁ = 3/4r

3/4r + 4r = 19
19/4r = 19 /:19/4
r = 4

a₁ = 3/4 * 4 = 3
1 5 1