Question

Find the values of s1 and d for an arithmetic sequence with s5= 10 and s8 = 22

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Answer 1

a. s1 = -6; d = 4

Explanation:

The difference between terms 3 apart will be 3 times the common difference:

d = (s8 -s5)/3 = (22 -10)/3 = 12/3 = 4

The difference between s1 and s5 will be 4 times the common difference, so ...

s1 = s5 -4d = 10 -4(4) = -6

These values match choice A: s1 = -6, d = 4.