Question

The 4th term of an AP is zero. Prove that its 25th term is triple its 11th term.

Class 10

Arithmetic Progressions

Answer 1

here is your answer
Given a4 = 0 
That is (a + 3d) = 0
 ⇒ a = - 3d
→ (1) nth term of AP is given by an = a + (n – 1)d a11
 = a + 10d = – 3d + 10d = 7d  [From (1)] 
a25 = a+ 24d = – 3d + 24d = 21d  [From (1)]  
      = 3 x 7d 
Hence a25 = 3 x a11
please mark as brainlist answer....

Answer 2

Hi friend
Your answer:
We have given that a4=0
We want to prove that :a25=3×a11
Proof: a4=0
a+3d=0
a= -3d......... (i)

a25=a+24d
Put value of a from eqn i
- 3d+24d
= 21d...........(ii)
a11=3 (a+10d)
3(-3d+10d)
=21d.........(iii)
From II and iii we get
a25=3×a11

I hope it helps you
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