Question

if the 9th term of an AP is 0 prove that 29th term is double of its 19th yerm

Answer 1

t9=0
a+8d=0. a=-8d. (1)
then we can prove that 29th term is double of 19th term
t29=a+28d
t19=a+18d
from from one substitute a equal to minus 8d
t29=-8d+28d
t29=20d
t19=-8d+18d
t19=10d