Question

If 7 times the 7th term of AP is equal to 11 times of its 11th term then find the 18th term

Answer 1

Answer:

Step-by-step explanation:

Firstly,

an=a+(n-1)d

7[a+(7-1)d]=11[a+(11-1)d]

7(a+6d)=11(a+10d)

7a+42d=11a+110d

7a-11a=110d-42d

-4a=68d

a= -68/4

a= -17d ----------------(1)

a18=a+(18-1)d

=a+17d

Put value of a from 1

a18= -17d+17d

=0

Eighteenth term of AP is 0