To Find: we need to find n when an = 0
Given: The series is 64, 60, 56, 52, 48, … and an = 0
a1 = 64, a2 = 60 and d = 60 – 64 = –4
(Where a = a1 is first term, a2 is second term, an is nth term and d is common difference of given AP)
Formula Used: an = a + (n - 1)d
an = 0 = a1 + (n –1)(– 4)
0 – 64 = (n –1)(– 4) [subtract 64 on both sides]
– 64 = (n –1)(– 4)
64 = (n –1)4 [Divide both side by '–']
16 = (n –1) [Divide both side by 4]
n = 17th [add 1 on both sides]
The 17th term of this AP is equal to 0.
