You have to look for f(x+y)=f(x)+f(y)

Solution has to be simple i.e. no squares, divisions, additions

If you don't immediatly see that E is the solution, plug in numbers

x=3, y=2

You will find that E is the right answer

Well, where is y? Are you saying to apply x for a, y for b? still I do not see how -3x applies to the given f(a+b)=f(a)+f(b)....help me there!
THANKS! :roll:

Sorry for using x, y .. was a,b

For f(x)=-3x

a=2
b=3

f(a+b)=f(5)=-3*5

f(a)+f(b)=-3*2+-3*3=-15

Therefore E is the right answer

Does not work for any function were x is x^2, 1/x as not linear

Try

For f(x)=x^2

a=2
b=3

f(a+b)=f(5)=5^2=25

f(a)+f(b)=2^2+3^2=13

or


For f(x)=2/x

a=2
b=3

f(a+b)=f(5)=2/5

f(a)+f(b)=2/2+2/3