Question

An = 5 × an-1 and a1 = 3.

What is a5
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A5 =​

Answer 1

`A_(5) = 1875`

Explanation:

The geometric sequence is represented by

`A_(n) = 5 * A_(n - 1)` .......... (1) and
`A_(1) = 3`

So,
`A_(2) = 5 * A_(2 - 1) = 5 * A_(1) = 5 * 3 = 15`

{Putting n = 2}

Again, putting n = 3 in equation (1), we get

`A_(3) = 5 * A_(2) = 5 * 15 = 75`

Again, putting n = 4 in equation (1), we get

`A_(4) = 5 * A_(3) = 5 * 75 = 375`

Again, putting n = 5 in equation (1), we get

`A_(5) = 5 * A_(4) = 5 * 375 = 1875` (Answer)