Graph of e^x
The graph of eˣ is the exponential curve with a remarkable property: at every point its slope equals its height. It crosses the y-axis at (0, 1), creeps along just above the x-axis to the left, and shoots upward to the right.
Key features
- Domain
- All real numbers
- Range
- y > 0
- Horizontal asymptote
- y = 0 as x → −∞
- Notable points
- (0, 1) and (1, e) with e ≈ 2.71828
- Monotonic
- Increasing everywhere
- Concavity
- Concave up everywhere
- Special property
- d/dx eˣ = eˣ
- y-intercept
- (0, 1)
- Derivative
- ex
- Antiderivative
- ex+C
Derivative and antiderivative from the calculator’s algebra system. Domain, range and asymptotes are stated for real x.
What the graph of eˣ looks like
e ≈ 2.71828 is the one base for which the exponential curve has slope exactly 1 where it crosses the y-axis. That single fact makes eˣ its own derivative: the slope of the graph at any point equals the y-value there.
To the left the curve gets arbitrarily close to the x-axis without touching it, since eˣ is positive for every x: e⁻⁵ ≈ 0.0067. To the right it doubles roughly every 0.693 units (ln 2), and eventually outgrows any power of x.
Reflecting the graph in the line y = x gives ln x, its inverse. Reflecting it in the y-axis gives e⁻ˣ, the shape of exponential decay.
Points of interest
Found numerically to about twelve digits in the window −5 ≤ x ≤ 3, then shown in exact form where one exists.
- x-intercepts (roots)
- None in this window
- Local maxima
- None in this window
- Local minima
- None in this window
- Inflection points
- None in this window
Table of values
A few points to plot, with exact values where they are simple.
| x | y = eˣ |
|---|---|
| −3 | 0.0497871 |
| −2 | 0.135335 |
| −1 | 0.367879 |
| 0 | 1 |
| 1 | e |
| 2 | 7.38906 |
| 3 | 20.0855 |
How to graph eˣ by hand
- 1Draw the horizontal asymptote y = 0 (the x-axis).
- 2Plot (0, 1), (1, 2.72), (2, 7.39) and (−1, 0.37).
- 3Draw an increasing curve through the points that bends upward, flattening toward the x-axis on the left without touching it.
- 4Check the slope at (0, 1): the curve should cross the y-axis at 45°.
Transformations
How the graph moves when you change the formula. The original is eˣ in blue.
y = e^(-x)Reflected in the y-axis: exponential decay.y = e^(x - 2)Shifted right 2: crosses the y-axis at e⁻² ≈ 0.135.y = e^x - 3Shifted down 3: the asymptote moves to y = −3 and the curve now crosses the x-axis at x = ln 3.
Where it shows up
- Continuous compound interest: P e^(rt).
- Population growth, radioactive decay and cooling, wherever the rate of change is proportional to the amount.
- The normal distribution, whose bell curve is built from e^(−x²/2).
Frequently asked questions
What is the domain and range of e^x?
Does e^x ever equal zero?
Why is e^x its own derivative?
What is the y-intercept of e^x?
Related graphs
Defined for x > 0, through (1, 0) and (e, 1).
y = aˣ: growth when a > 1, decay when 0 < a < 1.
Halves every step: (0, 1), (1, ½), (2, ¼), …
The bell curve: peak (0, 1), area √π.
The S-curve from 0 to 1, midpoint (0, ½).
The catenary: the shape of a hanging chain.
Change the window, add sliders for a, b, h and k, trace the curve with your keyboard, or overlay its derivative.