Taylor Series D644B6
1. **Problem statement:** Find the Taylor series expansion of the function $f(x) = e^{2x}$ around $x=0$ up to the $x^3$ term.
2. **Formula:** The Taylor series of a function $f(x)$ around $x=a$ is given by:
$$f(x) = \sum_{n=0}^\infty \frac{f^{(n)}(a)}{n!}(x - a)^n$$
where $f^{(n)}(a)$ is the $n$th derivative of $f$ evaluated at $x=a$.
3. Since we want the series around $x=0$, $a=0$, so:
$$f(x) = \sum_{n=0}^\infty \frac{f^{(n)}(0)}{n!} x^n$$
4. **Calculate derivatives:**
- $f(x) = e^{2x}$
- $f'(x) = 2e^{2x}$
- $f''(x) = 4e^{2x}$
- $f^{(3)}(x) = 8e^{2x}$
5. **Evaluate derivatives at $x=0$:**
- $f(0) = e^0 = 1$
- $f'(0) = 2e^0 = 2$
- $f''(0) = 4e^0 = 4$
- $f^{(3)}(0) = 8e^0 = 8$
6. **Write the Taylor series up to $x^3$ term:**
$$f(x) \approx f(0) + \frac{f'(0)}{1!}x + \frac{f''(0)}{2!}x^2 + \frac{f^{(3)}(0)}{3!}x^3$$
Substitute values:
$$= 1 + 2x + \frac{4}{2}x^2 + \frac{8}{6}x^3 = 1 + 2x + 2x^2 + \frac{4}{3}x^3$$
7. **Final answer:**
$$\boxed{f(x) \approx 1 + 2x + 2x^2 + \frac{4}{3}x^3}$$
This is the Taylor series expansion of $e^{2x}$ around $x=0$ up to the $x^3$ term.