Question

for an AP 2nd term is 12 and 14 term is 20 find the sum of first 25 terms

Answer 1

Given :
a + d = 12 -----------(1)
a +13d=20
by subtracting these two equations,
12d = 8
d = 2/3
putting this value in eq.1
a+2/3=12
a=12-2/3
a=34/3
an=a +(n-1)d
=34/3+24×2/3
=34/3+16
=82/3
Sn= n/2[a+an]
=25/2 [34/3+82/3]
=25/2 [116/3]
Sn=1450/3

Answer 2

here is ur answer....