If 3^(x+y)=81 & 81^(x-y)=3, then x=?

• x=17/8 ans.
  3^(x+y)=3^4 implies that
  x+y=4---(i)
  3^4(x-y)=3^1 implies that
  4x-4y=1---(ii)
  By solving two equations:
  x=17/8 ans.
• 11 years agoHelpfull: Yes(16) No(0)
• 17/8
  
  3^(x+y)=81 means x+y=4
  81^(x-y)=3 means x-y=1/4
  solving it, we get
  x= 17/8
  
  
• 11 years agoHelpfull: Yes(7) No(4)
• 3^(x+y)=3^4 & 3^4(x-y)=3^1
  x+y=4 & 4(x-y)=1
  y=4-x & 4(x-(4-x))=1
  4(x-4+x)=1
  4(2x-4)=1
  2x-4=1/4
  2x=1/4 + 4
  x=17/8
• 11 years agoHelpfull: Yes(2) No(0)
• x=17/8
  y=15/8
  
  3^(x+y)=3^4
  by comparing,
  x+y=4--------(1)
  
  81^(x-y)=3
  3^4(x-y)=3^1
  by comparing,
  4x-4y=1---------(2)
  
  4*(1)and (2)
  4x+4y=16
  4x-4y=1
  
  x=17/8
  y=15/8
• 11 years agoHelpfull: Yes(0) No(0)