Ubestemt integral

Ubestemt integral

Regn ut integralet

4xx2+2dx\int 4x\sqrt{ x^2+2 }\, dx
Fasit

43x2+2(x2+2)+C=43(x2+2)32+C\frac{4}{3}\cdot \sqrt{ x^2+2 } \cdot(x^2+2)+C=\frac{4}{3}(x^2+2)^{\frac{3}{2}}+C

Løsningsforslag
4xx2+2dx,u=x2+2    dudx=2x    du=2xdx2udu=2u12du=223u32+C=43(x2+2)32+C=43(x2+2)x2+2+C\begin{aligned} \int 4x\sqrt{ x^2+2 } \, \mathrm{d}x, \quad u=x^2+2 \implies \frac{du}{dx}=2x \iff du=2xdx\\ \int 2\sqrt{ u } \, \mathrm{d}u =2\int u^{\frac{1}{2}} \, \mathrm{d}u =2\frac{2}{3}u^{\frac{3}{2}}+C=\frac{4}{3}(x^2+2)^{\frac{3}{2}}+C'=\frac{4}{3}(x^{2}+2) \sqrt{ x^{2}+2 } + C' \end{aligned}