if f(1)=4,f(x+y)=f(x)+f(y)+7xy+2, for x>0,y>0 find f(2)+f(5)=?

• f(2)=17,f(3)=37,f(5)=98;
  f(2)+f(5)=115
• 10 years agoHelpfull: Yes(5) No(2)
• F(x+y)=f(x)+f(y)+7xy+2
  so
  f(1+1)=f(1)+f(1)+7*1*1+2
  =4+4+7+2
  =17
  f(2)=17
  f(2+2)=f(2)+f(2)+7*2*2+2
  =17+17+28+2
  =64
  f(4)=64
  f(4+1)=f(4)+f(1)+7*4*1+2
  =64+4+28+2
  =98
  f(5)=98
  now
  f(2)+f(5)= 17+98
  =115
• 9 years agoHelpfull: Yes(3) No(2)
• this is today's tcs exam question...
• 10 years agoHelpfull: Yes(1) No(1)
• ans is 158 + 17 = 175
• 10 years agoHelpfull: Yes(1) No(0)
• f([m/n]) = [m/n] f(1). so f(2)=2*f(1) and f(5)=5*f(1)
  link: http://www.maths.ox.ac.uk/files/study-guide/p2.2.e6.sol.html
• 10 years agoHelpfull: Yes(1) No(0)