Question

if the nth term of the AP 9, 7, 5... is same as the nth term of thr AP 15, 12, 9.... ; find n​

Answer 1

Answer:

In the 1st series 1st term a=9

common difference d=7-9= -2

nth term=a+(n-1)d

=9+(n-1).(-2)

=9-2n+2

=11-2n

In the 2nd series 1 st term a =15

common difference d=12-15= -3

nth term =a+(n-1) .d

=15+(n-1).(-3)

=15-3n+3

=18-3n

according to question

11 -2n= 18-3n

=> -2n+3n=18-11

=> n=7