Question

The Question is from Arithmetic progression....Answer fast plzzz...

Answer 1

Given:: t8 = 15

i.e.

a+7d=15 -----(1)

we have to find S15

S15=n/2 [2a +(n-1)d]

=15/2 [ 2a+14d]

= 15/2 × 2[a+7d] ...taking 2 common

= 15 × 15 .....from (1)

= 225 .

Sum of first 15 terms is 225

Answer 2

which subject it is tell me please