Question

In an AP, n = 14, d = -6, Sn = 301 find a.

Answer 1

here an = a +( n -1)d ..............1


in equation Sn = 14/2( 2a +(n-1)d)
Sn = 7(2a +13*(-6))
301 = 14a - 78
a = (301+ 78)/14
a = 379/14 = 22.23

Answer 2

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

301=14/2[2a+(14-1)-6]

301=7[2a-78]

301=14a-546

847=14a

a=60.5 ans.