Q. 64.7( 6 Votes )

The 21st term of an AP whose first two terms are - 3 and 4, is
A. 17

B. 137

C. 143

D. - 143

Answer :


first two terms of an AP are a = - 3 and a2 = 4.


As we know, nth term of an AP is


an = a + (n - 1)d


where a = first term


an is nth term


d is the common difference


a2 = a + d


4 = - 3 + d


d = 7


Common difference, d = 7


a21 = a + 20d


= - 3 + (20)(7)


= 137

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