Question

If nth term of an A.P is $(2n+1)$ , what is the sum of its first three terms?

Answer 1

$an=(2n+1)$

$a1=2\times 1+1=3$

$a1=3$

$a2=(2\times 2)+1$

$a2=5$

$a3=(2\times 3)+1$

$a3=7$

$Sumoffirstthreeterms=3+5+7$

$=15$