Integral Ln X
1. **State the problem:** We need to evaluate the integral $$\int x \ln x \, dx$$.
2. **Choose a method:** Use integration by parts, where $$\int u \, dv = uv - \int v \, du$$.
3. **Assign parts:** Let $$u = \ln x$$ and $$dv = x \, dx$$.
4. **Compute derivatives and integrals:**
- $$du = \frac{1}{x} \, dx$$
- $$v = \frac{x^2}{2}$$
5. **Apply integration by parts formula:**
$$\int x \ln x \, dx = \frac{x^2}{2} \ln x - \int \frac{x^2}{2} \cdot \frac{1}{x} \, dx = \frac{x^2}{2} \ln x - \frac{1}{2} \int x \, dx$$
6. **Integrate remaining integral:**
$$\int x \, dx = \frac{x^2}{2}$$
7. **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:**
$$\boxed{\int x \ln x \, dx = \frac{x^2}{2} \ln x - \frac{x^2}{4} + C}$$