Integral X Ln X
1. **State the problem:** We want to find the integral $$\int x \ln(x) \, dx$$.
2. **Formula and method:** We will use integration by parts, which states:
$$\int u \, dv = uv - \int v \, du$$
3. **Choose parts:** Let
$$u = \ln(x) \quad \Rightarrow \quad du = \frac{1}{x} dx$$
$$dv = x \, dx \quad \Rightarrow \quad v = \frac{x^2}{2}$$
4. **Apply integration by parts:**
$$\int x \ln(x) \, dx = \frac{x^2}{2} \ln(x) - \int \frac{x^2}{2} \cdot \frac{1}{x} \, dx = \frac{x^2}{2} \ln(x) - \frac{1}{2} \int x \, dx$$
5. **Integrate remaining integral:**
$$\int x \, dx = \frac{x^2}{2}$$
6. **Substitute back:**
$$\int x \ln(x) \, dx = \frac{x^2}{2} \ln(x) - \frac{1}{2} \cdot \frac{x^2}{2} + C = \frac{x^2}{2} \ln(x) - \frac{x^2}{4} + C$$
**Final answer:**
$$\boxed{\int x \ln(x) \, dx = \frac{x^2}{2} \ln(x) - \frac{x^2}{4} + C}$$