x^4+(1/x^4)=47 then x^3+(1/x^3)=?

• (x^2)^2+(1/x^2)^2 +2=47+2 (adding 2 to both sides)
  (x^2+1/x^2)^2=7^2
  x^2+1/x^2=7
  again adding 2 to both sides we get
  (x+1/x)^2=3^2
  x+1/x=3
  cubing above we get
  x^3+1/x^3+3(x+1/x)=27
  using value of x+1/x=3 in above equation we get
  x^3+1/x^3=27-9=18
• 7 years agoHelpfull: Yes(0) No(0)