How do you find the formula for $a_n$ for the arithmetic sequence $a_1=-y, d=5y$ ?

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Answer 1 · 2017-08-26T09:57:30

$u_n = (5n-6)y$

If we have $n$ terms of an AP, with first term $a$ , and common difference $d$ the terms are:

${a,a+d,a+2d,...,a+(n-1)d}$

Assuming $a_1$ is the first term (as opposed to $a_0$ ) then we have:

$a = -y$
$d = 5y$

So the $n^(th)$ term us:

$u_n = -y + (n-1)5y$
$\ \ \ \ = (5n-6)y$

How do you find the formula for a_na_n for the arithmetic sequence a_1=-y, d=5ya_1=-y, d=5y?