1. **Stating the problem:** We are asked to find the limits of the function
$$f(x) = (-x^3 + 2x^2) e^{-x+1}$$
as $x \to +\infty$ and as $x \to -\infty$.
2. **Recall the limit properties and behavior:**
- The exponential function $e^t$ grows very fast as $t \to +\infty$ and tends to zero as $t \to -\infty$.
- Polynomial terms grow slower than exponentials.
3. **Analyze the limit as $x \to +\infty$: **
Rewrite the function:
$$f(x) = (-x^3 + 2x^2) e^{-x+1} = (-x^3 + 2x^2) e^{1} e^{-x}$$
As $x \to +\infty$, $e^{-x} \to 0$ very fast, while $-x^3 + 2x^2$ grows large in magnitude but polynomially.
Therefore, the product tends to zero:
$$\lim_{x \to +\infty} f(x) = 0$$
4. **Analyze the limit as $x \to -\infty$: **
Rewrite the exponential term:
$$e^{-x+1} = e^{1 - x} = e^{1} e^{-x}$$
As $x \to -\infty$, $-x \to +\infty$, so $e^{-x+1} \to +\infty$.
The polynomial part:
$$-x^3 + 2x^2$$
For large negative $x$, $-x^3$ dominates. Since $x^3$ is negative for negative $x$, $-x^3$ is positive and very large.
So both parts tend to $+\infty$, thus:
$$\lim_{x \to -\infty} f(x) = +\infty$$
**Final answers:**
$$\boxed{\lim_{x \to +\infty} f(x) = 0, \quad \lim_{x \to -\infty} f(x) = +\infty}$$
Limits Infinity A4Ed8C
Step-by-step solutions with LaTeX - clean, fast, and student-friendly.