Question

the 4th term of an ap is zero prove that 25th term of an ap is thrice 3 times its 11 term

Answer 1

Acc to ques 
    a₄ = 0  
a+3d = 0
      a = -3d                                             -----------------1
Then also to prove a₂₅=3(a₁₁)
So it would be
  a + 24d = 3(a + 10d)                            ------------------2
From 1 and 2
    -3d + 24d = 3(-3d+10d)
             21d = 3(7d)
             21d = 21d
  
LHS=RHS

HENCE PROVED 

:) Hope this helps!!!!!

Answer 2

I think it is right answer