Question

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

Answer 1

Answer:

T18 = 0

Step-by-step explanation:

WE can see that : 7 × T7 = 11 × T11

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

7a + 42d = 11a + 110d

7a − 11a = 110d − 42d

−4a = 68d

∴a = −17d

Consider, T18 = a + 17d = −17d + 17d

∴T18 = 0