# function

golfer1
Posers and Puzzles 15 Apr '08 22:48
1. 15 Apr '08 22:48
f(x)= 2 for all real numbers x. What is f(x+2)?
2. 15 Apr '08 22:53
2
3. AThousandYoung
16 Apr '08 00:05
Originally posted by GregM
2
Unless x is not a real number...
4. joe shmo
Strange Egg
16 Apr '08 00:211 edit
Originally posted by golfer1
f(x)= 2 for all real numbers x. What is f(x+2)?
I case you dont know f(x)= 2 is a horizantal line. the (+2) technically shifts the graph of f(x) =2 to the left 2 units, but on a horizantal line nothing happens, so in general f(x + a ) = 2 for all real numbers a....

or at least I hope so..lol
5. 16 Apr '08 09:33
yeah, but consider a slight modification of the Dirichlet's function

f(x) = 2 if x is real, and f(x) = 0 if x is complex ... now you have two answers...

or f(x) = 2 if x is real, and f(x) = Re(x) if x is complex ... now the range of the function is the entire R.

in other words, the question as posed is incomplete, without stating the domain of the original function.
6. forkedknight
Defend the Universe
21 Apr '08 16:231 edit
Originally posted by 3v1l5w1n
yeah, but consider a slight modification of the Dirichlet's function

f(x) = 2 if x is real, and f(x) = 0 if x is complex ... now you have two answers...

or f(x) = 2 if x is real, and f(x) = Re(x) if x is complex ... now the range of the function is the entire R.

in other words, the question as posed is [b]incomplete
, without stating the domain of the original function.[/b]
generally when someone says f(x) = ..., for all real numbers x, I assume R to be the domain.
7. 22 Apr '08 02:18
Real numbers fall within the realm of complex numbers, because any real number R could be written as R + 0i.

If x is real, then x+2 is also real, and hence f(x+2) = 2.

F(x) + 2 would equal 4, however.
8. 23 Apr '08 23:17
Solve this f:R->R

f(x^2+y^2+2f(xy)=f(x+y)^2

for all reals x,y

have fun! Three solutions
9. 23 Apr '08 23:37
Missing an end parentheses on that equality.

It would be useful to know where it is before solving begins.
10. 24 Apr '08 00:03
Very sorry:
Solve this f:R->R

f(x^2+y^2+2f(xy))=f(x+y)^2

for all reals x,y
11. 24 Apr '08 02:42
I can find 3 solutions.

f(x) = 0
f(x) = 1
f(x) = x

I do not know how to prove those are the only 3 solutions, or indeed if others may exist.
12. 24 Apr '08 09:53
There is another solution, which includes f(x)=1
f(x)=1 for all x>=-2/3 and |f(x)|=1 for all x