Question

In an AP, if an = 2n - 3 find a3 ​

Answer 1

If Tn=2n+3 then,

T1=(2×1)+3=2+3=5

T2=(2×2)+3=4+3=7

T3=(2×3)+3=6+3=9

Therefore, S3 is the sum of T1, T2 and T3 that is:

S3=T1+T2+T3=5+7+9=21

Hence, a3=21.