Asked by Alisha

Find the first three terms of an arithmetic series in which the fifteenth term is –7 and the sum of the first fifteen terms is 210
Answered by Reiny
fifteenth term is –7 -----> a+14d = -7 **

the sum of the first fifteen terms is 210
----> (15/2)(2a + 14d) = 210
2a + 14d = 28 ***

subtract ** from ***
a = 35
back in **,
a + 14d = -7
35+14d = -7
d = -3

Now form the first 3 terms
Answered by Alisha
what is the equation??
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