SOLUTION: determine the arithmetic series given S4 = 26 s5= 42 and s6 = 57

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Question 838144: determine the arithmetic series given S4 = 26 s5= 42 and s6 = 57
Answer by mananth(16946) About Me  (Show Source):
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S4 = 26 s5= 42 and s6 = 57
S5-S4=T5
T5=42-26=16
S6-S5=T6
T6= 57-42=14
T5=16, T6=14
T6-T5= = d the common difference
=-2
Tn = a+(n-1)*d
T6= 14
14= a+(6-1)*-2
14=a-10
a=14+10
a=24
a= 24 d=-2
so the series is 24,22,20,18,16,14,12,.......