Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**Hannibal lecter****Member**- Registered: 2016-02-11
- Posts: 208
- Website

Hi, is there a root for the f(x) = e^-x ???

is it close to 0.571143115080177? or that wrong there is no any root?

please help me

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

**ganesh****Administrator**- Registered: 2005-06-28
- Posts: 23,991

Hi,

Hope this graph helps:

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

Hannibal lecter wrote:

raised to the power of anything won't ever have a root, because the exponential function is always positive. You can see this in the graph that ganesh posted -- it won't ever touch (nor go below) the x-axis.Hi, is there a root for the f(x) = e^-x ???

is it close to 0.571143115080177? or that wrong there is no any root?

please help me

Where did you get 0.571143115080177 from? Are you stating the problem correctly? Or is something else meant by the word 'root' here?

**LearnMathsFree: Videos on various topics.New: Integration Problem | Adding FractionsPopular: Continued Fractions | Metric Spaces | Duality**

Offline

**Hannibal lecter****Member**- Registered: 2016-02-11
- Posts: 208
- Website

I tried a matlab code to solve it, but thanks for helping I know it's nor have a root now..

but what about exp(-x)=x?

Wisdom is a tree which grows in the heart and fruits on the tongue

Offline

**iamaditya****Member**- From: Planet Mars
- Registered: 2016-11-15
- Posts: 762

zetafunc wrote:

Where did you get 0.571143115080177 from?

See the graph which Ganesh posted. You will see that it converges down to X-axis and almost touches it at that value.

Practice makes a man perfect.

There is no substitute to hard work

All of us do not have equal talents but everybody has equal oppurtunities to build their talents.-APJ Abdul Kalam

Offline

**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,273

See here:

http://www.mathsisfun.com/data/function … nc1=e^(-x)

Just add y = x as the second function and you'll see it does have that value as the solution.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

iamaditya wrote:

See the graph which Ganesh posted. You will see that it converges down to X-axis and almost touches it at that value.

No, it doesn't ever touch the x-axis. The exponential function is strictly positive: it can't have any roots.

However, if we take , then there is indeed a root. In fact, if we allow complex solutions, there are infinitely many of them, and they are precisely the nth values of the Lambert-W function, . This sequence generates all the complex roots.There is one real root, the so-called Omega constant, . There are several exact forms for the Omega constant, such as the 'power tower':and a nice integral relation is:

**LearnMathsFree: Videos on various topics.New: Integration Problem | Adding FractionsPopular: Continued Fractions | Metric Spaces | Duality**

Offline

Pages: **1**