If 7 times the 7 th term of an
a.P. Is equal to 11 times the 11th term of the
a.P., find its 18th term
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Answer:
a=first term
d=common difference
GIVEN-
7(7th term)=11(11th term)
7(a+6d)=11(a+10d)
7a+42d=11a+110d
11a-7a=42d-110d
4a=-68d
a=-17d........equation 1
18th term=a+17d
=-17d+17d (from equation1)
=0
18th term=0.
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