Question

show that a1,a2,....,an,... from an AP where an is defined as below (1) an=3+4n (2)=9-5n Also find the sum of the 15th terms in each case​

Answer 1

this answer of your questions

Answer 2

I) an=3+4n

if n=1,

a1=3+4(1)

=3+4

a1=7

if n=2

a2=3+4(2)

=3+8

a2=11

if n=3

a3=3+4(3)

=3+12

a3=15

a. p is. 7,11,15.... a=7,,, d=4

a15=a+(n-1)d

=7+(15-1)4

=7+(14)4

=7+56

a15=63

sum;

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

s15=63/2(2x7+(63-1)4)

=63/2(14+(62)4)

=63/2(14+248)

=63/2(262)

=63(131)

s15=8253