2) Write a formula for the nth term of each arithmetic sequence. Then use the formula to find a15.?

Question

a. 3, 8, 13, 18
b. a1 = –3 and d = 6

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Answer 1 · 2018-04-14T17:15:05

$a_{15} =$ $a_15=$ 81

formula for $n t h$ $nth$ term is
$a_{n} = a_{1} + (n - 1) d$ $a_n= a_1+(n-1)d$

a)
nth term is
$a_{n} = 3 + (n - 1) 5$ $a_n=3+(n-1)5$
[from given series $a = 3$ $a=3$ , $d = 5$ $d=5$ ]

b)
given $a_{1} = - 3$ $a_1=-3$ , $d = 6$ $d=6$ so

$a_{n} = - 3 + (n - 1) 6$ $a_n= -3+(n-1)6$

$a_{15} = - 3 + (15 - 1) 6$ $a_15=-3+(15-1)6$

$a_{15} = - 3 + 84$ $a_15=-3+84$

$a_{15} = 81$ $a_15=81$