Question

If 7 times the 7th term of an AP is equal to 11th term,then it's 18th term will be (a) 7,(b) 11,(c) 18,(d) 0​

Answer 1

Given :-

→ 7a7 = 11

▶ To prove :-

→  a18 = 0 .

We have,

=> 7a7 = 11a7

=> 7( a + 6d ) = 11( a + 10d ) .

=> 7a + 42d = 11a + 110d .

=> 11a - 7a = 42d - 110d .

=> 4a = - 68d .

=> 4a + 68d = 0 .

=> 4( a + 17d ) = 0 .

=> a + 17d = 0/4 .

=> a + ( 18 - 1 )d = 0.

a18=0

✔✔ Hence, it is proved