Q2 of 69 Page 78

Find the fourth term from the end in an A.P. – 11, – 8, – 5, . . ., 49.

First term from end a = 49

tn = – 11


tn – 1 = – 8


Common difference d = tn – tn – 1 = – 11 – ( – 8) = – 11 + 8 = – 3


Now, By using nth term of an A.P. formula


tn = a + (n – 1)d


where n = no. of terms


a = first term


d = common difference


tn = nth terms


no. of terms n = 4


⇒ t4 = 49 + (4 – 1) × ( – 3)


⇒ t4 = 49 + 3 × ( – 3)


⇒ t4 = 49 – 9 = 40


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