SOLUTION: The first,third and eight term of an arithmetic sequence form the first three terms of a geometric sequence. if the first term is 4. Find the common difference of the arthimetic se

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Question 848905: The first,third and eight term of an arithmetic sequence form the first three terms of a geometric sequence. if the first term is 4. Find the common difference of the arthimetic sequence
Answer by richwmiller(17219) About Me  (Show Source):
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an = a + (n - 1)d
a1 = a
a3 = a + (2)d
a8 = a + (7)d

Geometric
Tn = t * r^(n - 1)
a= t
4 + 2d= 4 * r
4 + 7d= 4 * r^(2)
d = 3, r = 5/2
or
d = 0, r = 1