IF the nth term of an AP is (2n +1) then the sum of its first three terms is
(a) 6n +3 (b) 15 (c) 12 (d) 21

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Solution

If nth term of an A.P = 2n+1

then, first term of A.P = 2(1)+1
= 2+1
= 3

then, second term = 2 (2) + 1

》4+1

》5

third term = 2 (3) +1

》6+1

》7

sum of terms = 3+5+7

sum of terms = 15
option b is correct

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