TCS Company Numerical Ability Algebra

Suppose that the function f is defined on natural numbers (integers>0) such that f(1)=1 &f(x+y)=f(x)+f(y)+3xy+3 for all x,y.whart is the value of f(5)+f(7)? A)140 b)215 c)135 d)129

Read Solution (Total 3)

f(1)=1
f(2)=f(1)+f(1)+3*1*1+3=8

f(3)=f(1)+f(2)+3*1*2+3=1+8+6+3=18

f(4)=f(1)+f(3)+3*1*3+3=1+8+6+3=1+18+9+3=31

f(5)=f(1)+f(4)+3*1*4+3=47
f(7)=f(4)+f(3)+3*4*3+3=88

Hence f(5)+f(7)=135
8 years agoHelpfull: Yes(9) No(0)

Ans : 135
f (1)-1
f (2)-8
f(4)-31
f(5)-47
f (7)-88

F (5)+f (7) - 135
8 years agoHelpfull: Yes(2) No(2)
YEs it is Exactly 135.
8 years agoHelpfull: Yes(0) No(1)

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