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