Question

If the sum of an Ap is 5n+n2 find the 10th term and 13term

Answer 1

***********************************************************Step-by-step explanation:

Answer 2

Answer:

a10 = 24 and a13 = 30

Step-by-step explanation:

AP is

Sn=5n+n², a10=?, a13=?

For n=1

∴S1=5×1+1²=5+1=6

∴a=6

For n=2

S2=5×2+2²=10+4=14

a2=S2-S1=14-6=8

∴a2=8

For n=3

S3=5×3+3²=15+9=24

a3=S3-S2=24-14=10

∴a3=10

Hence our AP is 6, 8, 10....

Now, a=6 and d=2 (∵8-6=2 & 10-8=2) and an=a+(n-1)d

∴a10=6+(10-1)2=6+9×2=6+18=24

and a13=6+(13-1)2=6+12×2=6+24=30

Hence, a10 = 24 and a13 = 30