Question

in an A.P 7(a7)=11(a11) then which term of its zero

Answer 1

hey mate
we have 7(a7)=11(a11)
general formula to find nth term of ap is
An=a +(n-1)d
so according to condition given in question
7(a+6d)=11(a+10d)
u will 4a+68d=0( eq 1)

so divide the equation by 4
u will get ->a+17d
n-1=17 ( from eq 1)
n=18
so its 18th term which is zero
i hope u understood!!

Answer 2

given, 7(a+6d) = 11(a+10d)
==>7a + 42d = 11a + 110d
11a - 7a = 42d - 110d
4a = -68d
a = -17d
a + 17d = 0
==>a18 = 0
i.e., the 18th term of the AP is zero