# Which of the following is/are true?

1. Jun 5, 2015

### Jaco Viljoen

1. The problem statement, all variables and given/known data
Which of the following statements are true?
A)
If f(x)=ex, then f(x)⋅f(-x)=1

B)
If g(x)=1/x, then g (1/x)=x

C)
If h(x)=√(x+2), then h(2)=±2

2. Relevant equations

3. The attempt at a solution
Only B

2. Jun 5, 2015

### Staff: Mentor

I agree, but why do you think that A and C are not true?

3. Jun 5, 2015

### Jaco Viljoen

A) doesn't seem to make sense to me... although x is still unknown.
C)The answer would be 2 not ±2.

4. Jun 5, 2015

### Staff: Mentor

But even without having a specific value for x, can't you evaluate f(x) - f(-x), to see whether it comes out to 1? Otherwise your answer is nothing more than a guess.
Yes.

5. Jun 5, 2015

### Jaco Viljoen

If f(x)=ex, then f(x)⋅f(-x)=1 Not true:
-ex

6. Jun 5, 2015

### Ray Vickson

In (A), it looks to me as though you are writing (i): $f(x) \times f(-x)$, while Mark44 seems to see (ii): $f(x) - f(-x)$. Which do you mean: (i) or (ii)?

7. Jun 5, 2015

### Staff: Mentor

Oops! My mistake! Thanks for pointing out my error, Ray. I misread that dot as a minus sign. f(x) X f(-x) is indeed equal to 1.