if 7 times the 7th term of an A. P is equal to 11 times its 11th term then find is 18th term
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Hi dr.....
HERE IS UR ANSWER:
7th term = (a+6d) 11th term = (a+10d)
(a+6d)7 since 7th term of the ap is 7 times and the same for 11th term
(a+6d)7=(A+10d)11 (given)
7a + 42d =11a +110d (on solving)
7a - 11a = 110d - 42d
-4a = -68d
a= -17d
we know 18th term = (a+17d)................................. (i)
now we substitute the value of a in (i)
which emplies,
-17d + 17d
= 0
hence proved...
HOPE THIS HELPS...
HERE IS UR ANSWER:
7th term = (a+6d) 11th term = (a+10d)
(a+6d)7 since 7th term of the ap is 7 times and the same for 11th term
(a+6d)7=(A+10d)11 (given)
7a + 42d =11a +110d (on solving)
7a - 11a = 110d - 42d
-4a = -68d
a= -17d
we know 18th term = (a+17d)................................. (i)
now we substitute the value of a in (i)
which emplies,
-17d + 17d
= 0
hence proved...
HOPE THIS HELPS...
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Answered by
4
7th term = (a+6d) 11th term = (a+10d)
(a+6d)7 since 7th term of the ap is 7 times and the same for 11th term
(a+6d)7=(A+10d)11 (given)
7a + 42d =11a +110d (on solving)
7a - 11a = 110d - 42d
-4a = -68d
a= -17d
we know 18th term = (a+17d)................................. (i)
now we substitute the value of a in (i)
which emplies,
-17d + 17d
= 0
hence proved.
(a+6d)7 since 7th term of the ap is 7 times and the same for 11th term
(a+6d)7=(A+10d)11 (given)
7a + 42d =11a +110d (on solving)
7a - 11a = 110d - 42d
-4a = -68d
a= -17d
we know 18th term = (a+17d)................................. (i)
now we substitute the value of a in (i)
which emplies,
-17d + 17d
= 0
hence proved.
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