# Is it possible

## Main Question or Discussion Point

Is it possible for f(x) to be equal to f '(x)? I've been trying all day to make it work and have gotten nothing.

Thanks

rock.freak667
Homework Helper
Is it possible for f(x) to be equal to f '(x)? I've been trying all day to make it work and have gotten nothing.

Thanks
Sure, if f(x)=ex, then f'(x) = ex = f(x).

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Oh, didn't think about that. XD I kept trying Trig to make it work....

Are there any other ways?

rock.freak667
Homework Helper
Oh, didn't think about that. XD I kept trying Trig to make it work....

Are there any other ways?
if you solve the differential equation

f'(x)=f(x)

You'd see that any multiply of ex would satisfy the condition. I think that is the only function, that I know of anyhow.

Indeed, every function of the form $$f(x)=Ce^x$$, with $$C\in \mathbb{R}$$ will do. There are no other functions that equal it's own derivative...