If (a^4)+(1/a^4)=119 then find value of (a^3)-(1/a^3)=????

• (a^4)+1/(a^4)=(a*a+1/a*a)(^2)-2=119
  after solving we get as
  (a-1/a)=3
  so the value of (a^3)-(1/a^3)=(3)(1+11)=36
  so ans is 36
• 9 years agoHelpfull: Yes(49) No(7)
• (a^4 + 1/a^4) = 119
  (a^2 + 1/a^2)^2 = 119 + 2 = 121 => a^2 + 1/a^2 = 11
  another eqn,
  (a - 1/a) = sqrt(9) = 3
  
  now,
  a^3 - 1/a^3
  = (a - 1/a)*(a^2 + a*1/a + 1/a^2)
  = 3*(11+1)
  = 36
• 9 years agoHelpfull: Yes(27) No(0)
• a^4+1/a^4=119
  (a^2+1/a^2)^2-2.a.1/a=119
  a^2+1/a^2=11
  (a-1/a)^2+2.a.1/a=11
  a-1/a=3
  
  Now we Know a3 - b3 = (a - b)3 + 3 a b (a - b)
  so,
  (a^3)-(1/a^3)=(a-1/a)^3-3*a*1/a(a-1/a)=3^3-3*3=27-9=18
  So the answer is 18
• 9 years agoHelpfull: Yes(26) No(22)
• a-1/a=3;
  a^2+1/a^2=11;
  so,
  a^3-1/a^3=36
• 9 years agoHelpfull: Yes(1) No(0)
• Aaproxmatly 36
• 9 years agoHelpfull: Yes(1) No(1)
• 36 is the correct answer
• 9 years agoHelpfull: Yes(1) No(0)
• (a+b)^2= a^2+b^2+2ab
  put b=1/a
  
  (a+1/a)^2=a^2+1/a^2+2
  
  (a+1/a)^2-2=a^2+1/a^2
  use this formula u will get the answer=36
  firstly +2 use u will get 121
  & then -2 use u will get 9
• 9 years agoHelpfull: Yes(1) No(0)
• CANNOT BE DETERMINED??
• 9 years agoHelpfull: Yes(0) No(3)
• Ans- 36 is correct..This question came in Bank exam SBI PO-2013.
• 9 years agoHelpfull: Yes(0) No(0)
• (a^4)+1/(a^4)=(a*a+1/a*a)(^2)-2=119
  after solving we get as
  (a-1/a)=3
  so the value of (a^3)-(1/a^3)=(3)(1+11)=36
  so ans is 36
  Read more at http://www.m4maths.com/placement-puzzles.php?ISSOLVED=&page=2&LPP=10&SOURCE=Elitmus&MYPUZZLE=&TOPIC=Numerical%20Ability&SUB_TOPIC=Number%20System#jY5PTuA3E8PZQx3c.99
• 9 years agoHelpfull: Yes(0) No(0)
• (x^2+1/x^2)^2 = x^4 + 1/x^4 + 2*x^2*1/x^2
  = 119 +2
  = 121
  x^2+1/x^2 = 11
  (x ­ 1/x)^2 = x^2 + 1/x^2 ­ 2*x*1/x
  = 11 ­2
  = 9
  x ­ 1/x = 3
  now (x­1/x)^3 = x^3 ­ 1/x^3 ­3*x*1/x(x ­1/x)
  so x^3 ­ 1/x^3 = 3^3 + 3*3
  = 27 +9
  = 36
  final ans is 36
  
• 8 years agoHelpfull: Yes(0) No(0)