CIĄGI !!!
Załóżmy,że ciąg (an) jest arytmetyczny:
a) znajdź różnicę ciągu oraz a1 , jeśli a5=-8 i a9=-2.
P.S. - ma wyjść r=3/2 , a1=-14
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an = a1 + (n - 1) * r
a5 = a1 + (5 - 1) * 4 = a1 + 4r
a9 = a1 + (9 - 1) * r = a1 + 8r
a5 = -8
a9 = -2
a1 + 4r = - 8
a1 + 8r = -2 /*(-1)
a1 + 4r = -8
-a1 - 8r = 2
-----------------
-4r = -6
r = (-6) / (-4)
r = 3/2 ---------- odpowiedź
a1 + 4r = - 8
a1 + 4 * 3/2 = -8
a1 + 6 = - 8
a1 = -8 - 6
a1 = - 14 ------------ odpowiedź