Question

if 9th of an Arthemthic progression is 0, prove that its 29th term is double the 19th term

Answer 1

Concept used :

nth term of an AP = a + (n-1)d

Step-by-step explanation:

Given,

9th term = 0

=> a + 8d = 0

=> a = -8d ----------(1)

Now,

29th term = a + 28d= -8d + 28d = 20d

(from eq 1 )

29th term = 20d --------(2)

19th term = a + 18d = -8d + 18d = 10d

(from eq 1 )

19th term = 10d --------(3)

from (2) and (3)

29th term = 2 x 19th term

hence proved