f(x)= 2(x) +1, f(f(f(f….f(n))))12 times = 81919 then n=?

• f(f(x))=f(2x+1)=4x+2+1----->2 times
  f(f(f(x)))=8x+4+2+1----------->3times
  similarly for 12 times is
  2^12(x)+2^11+2^10+.................+2^0=81919
  
  on solving this
  we get
  x=19
  
  Ans:x=19
• 9 years agoHelpfull: Yes(4) No(1)
• somebody solve it
• 9 years agoHelpfull: Yes(0) No(0)
• Let us find f(f(x)) first:
  f(f(x))= 2(2(x)+1) +1 =2^2(x)+3 = 2^2(x) + (2^2-1) Similarly find f(f(f(x))) we get it as 2^3(x) + (2^3 -1)
  That implies f(f(f(.....f(n))) 12 times = 2^12(n) + (2^12 -1) On solving we get 'n'=19
• 8 years agoHelpfull: Yes(0) No(0)