Question

The sum of first 16 terms of an A. P. 10,6,2,......is ​

Answer 1

using formula Sn =n/2 ×2a+n-1×d....we get sum 16 terms as -320....therefore S16is equal to -320

Answer 2

AP-10,6,2......

Sn=n/2 (2a+(n-1)d)

S16=16/2 (2×10+(16-1)-4)

S16=8 (20+15×(-4))

S16=8 (20-60)

S16=8×(-40)

S16=-320