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Question
Find the 23rd term of the following A.P.: 9, 4,-1,-6,-11.
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Solution
9, 4,-1,-6,-11
a = 9 , d = 4 - 9 = -5 , n = 23
tn = a + (n - 1) d
t23 = 9 + (23 - 1)(-5)
= 9 + 22 × -5
= 9 - 110
= -101
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