Find an expression in terms of n, for the nth term of the sequence 17, 14, 11, 8, 5, ...
The answer is 20 - 3n
But I do not understand why the answer is that so could anyone explain it to me? Thanks a lot!
2007-09-06 23:04:53 · 4 answers · asked by ♪£yricảl♪ 4 in Science & Mathematics ➔ Mathematics
d = - 3
a = 17 is 1st term
a(n) is nth term
a(n) = a + (n-1) d
a(n) = 17 + (n - 1)(-3)
a(n) = 17 - 3n + 3
a(n) = 20 - 3n
2007-09-07 03:51:56 · answer #1 · answered by Como 7 · 1⤊ 0⤋
In general, for a question like that
17, 14, 11, 8, ...
It's decreasing in steps of 3, so the answer should be something (say, X) minus 3 times n (the sequence count)
So:
(X - 3n) = value
But, since when n=1, value = 17
(X - 3) = 17
X = 20
So the sequence follows:
(20 -3n) = value
2007-09-06 23:21:25 · answer #2 · answered by taq2007 2 · 0⤊ 1⤋
the first term is, 20 - (1*3) = 17
the second term is, 20 - (2*3) = 14
the third term is, 20 - (3*3) = 11
........
so the nth term will be 20 - (n*3) = 20 - 3n
(just look at the patterns)
2007-09-06 23:11:38 · answer #3 · answered by tsunamijon 4 · 0⤊ 0⤋
term 1-> 17 = 20 -1*3
term 2-> 14 = 20-2*3
term 3-> 11 = 20-3*3
.....................................
term n-> 20-3n=20-n*3
2007-09-06 23:13:05 · answer #4 · answered by i_am_the_next_best_one 5 · 0⤊ 0⤋