Question

What are the first three terms of a geometric sequence in which a5 = 25 and the common ratio is 5?

Answer 1

Answer:  First three terms are 1/25, 1/5, and 1 in that order.

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Explanation:

The fifth term is 25, which makes the fourth term to be 25*(1/5) = 5. We multiply any term by the reciprocal of the common ratio to move back to the previous term.

The third term is 5*(1/5) = 1. The second term is 1*(1/5) = 1/5. The first term is (1/5)*(1/5) = 1/25

Therefore, the first five terms are:

1/25, 1/5, 1, 5, 25

As we move from left to right, we multiply each term by 5. Going in reverse, we multiply by 1/5.