Mathematics
Show that the progression 11, 5, -1, -7, -13,……..is an A.P. Write down its
(i) first term
(ii) common difference
(iii) 12th term.
AP
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Answer
Since, 5 - 11 = -6, -1 - 5 = -6, -7 - (-1) = -6 and -13 - (-7) = -6.
Hence, the series is an A.P. with common difference = -6.
We know that nth term of an A.P. is given by,
⇒ an = a + (n - 1)d, where a is the first term.
⇒ a12 = 11 + (12 - 1).(-6)
= 11 + 11(-6)
= 11 - 66
= -55.
Hence, a = 11, d = -6 and a12 = -55.
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