# Math Help - question about exponential function - based on Wikipedia

1. ## question about exponential function - based on Wikipedia

hi guys,

I am wondering why the "the sum of the first n + 1 terms of the power series of the exponential function gives negative numbers"

Exponential function - Wikipedia, the free encyclopedia - the figure on the right

I am also not so good to understand the exponential function itself... but I hope someone could help me!

THANK YOU

I am wondering why the "the sum of the first n + 1 terms of the power series of the exponential function gives negative numbers"
What does the sentence in red above mean?

3. Plate do you know a bit of Matlab? I think I will able to explain you better with the code...

Plate do you know a bit of Matlab? I think I will able to explain you better with the code...
Is this a mathematics question or a programing question?
If it is the latter, then I have no interest in it.
If it is the former, then you have no need any code.

hi guys,

I am wondering why the "the sum of the first n + 1 terms of the power series of the exponential function gives negative numbers"

Exponential function - Wikipedia, the free encyclopedia - the figure on the right

I am also not so good to understand the exponential function itself... but I hope someone could help me!

THANK YOU
If I understand your question correctly, you are asking why the first few terms of the infinite series for the exponential function -- for example,
$1 + x + \frac{1}{2!} x^2 + \frac{1}{3!} x^3$
can take on negative values although the exponential function $e^x$ is always positive.

The reason is that the series only gives the exponential function in the limit. If you truncate the series and only take finitely many terms, you only get an approximation to $e^x$, and actually the approximation is only a good fit for values near zero. If you get far away from zero the approximation is poor, and you can get negative values. The more terms in the series you take, the better the approximation gets, and you can get further away from zero before you get in trouble. That's what the animated graph on Wikipedia is trying to show.