Mathematics
Find the A.P. whose nth term is 7 - 3n. Also find the 20th term.
AP GP
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Answer
Given, an = 7 - 3n (Eq 1)
Putting n = 1, 2, 3, 4, …. in (Eq 1), we get
a1 = 7 - 3 × 1 = 7 - 3 = 4, a2 = 7 - 3 × 2 = 7 - 6 = 1
a3 = 7 - 3 × 3 = 7 - 9 = -2, a4 = 7 - 3 × 4 = 7 - 12 = -5, …
∴ Series = 4, 1, -2, -5 …..
Putting n = 20, for 20th term we get,
a20 = 7 - 3 × 20 = 7 - 60 = -53.
Hence, the A.P. is 4, 1, -2, -5 ….. and the 20th term is -53.
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