Question

If the 9th term of an AP is 0. So prove that 29th term is double the 19term.?

Answer 1

Let the first term of an A.P. = a
And common difference = d
Given: 9^th term of an A.P. is 0. Therefore,
a+(9-1)d=0
a=-8d

We have to prove that T29=2×T19
so,
T29=a+(29-1)d=a+28d
T19=a+(19-1)d=a+18d
a+28d=-8d+28d=20d
a+18d=-8d+18d=10d
thus proved