If 7 times the 7th term of an AP is equal to 11 times its 11th term, what is the value of 18th term?

Question

The sequence k, k^2, 16, k^3 has four terms in which first three terms are in GP.
What should be added in fourth term to get the last 3 terms in AP ?

Answer 1

0

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if 7*a7= 11*a11
a18=?

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7*( a + 6d ) = 11*( a + 10d ) => 7a + 42d = 11a + 110d => a + 17d = 0 .
a18 = a+17d=0 as above
a18=0