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An arithmetic sequence has first term a and common difference d. The sum of the first 25 terms is 15 times the sum of the first 4 terms.
1) Find a in terms of d.
2) Find the 55th term in terms of a.​

Respuesta :

Step-by-step explanation:

1) sum of the first 25 terms = 25a + 300d

sum of the first four terms = 4a + 6d

25a + 300d = 15(4a +6d)

25a +300d = 60a + 90d

210d = 35a

a = 6d

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