7^a+4 * 5^b =1715 then ab=?

• 1715=343*5
  =>7^a+4*5^b=7^3*5^1
  =>a+4=3, b=1
  =>a=-1
  ab=-1
• 10 years agoHelpfull: Yes(14) No(9)
• prime factorisation of 1715=7^3+5^1
  
  Now write:
  7^(a+4)*5^b=7^3+5^1
  compare L.H.S and R.H.S ,
  a+4=3, b=1;
  a=-1,b=1
  ab=-1
• 9 years agoHelpfull: Yes(3) No(1)
• pls share how 7^a+4*5^b=7^3*5^1 become?
• 10 years agoHelpfull: Yes(2) No(1)
• 1715=7*7*7*5
  that means 7^3 * 5^1
  Now write:
  7^(a+4)*5^b=7^3+5^1
  compare L.H.S and R.H.S ,
  a+4=3, b=1;
  a=-1,b=1
  ab=-1
• 7 years agoHelpfull: Yes(0) No(0)