Ubestemt integral
Regn ut integralet
\[\int 4x\sqrt{ x^2+2 }\, dx \]
Fasit
\(\frac{4}{3}\cdot \sqrt{ x^2+2 } \cdot(x^2+2)+C=\frac{4}{3}(x^2+2)^{\frac{3}{2}}+C\)
Løsningsforslag
\[\begin{aligned} \int 4x\sqrt{ x^2+2 } \, \mathrm{d}x, \quad u=x^2+2 \implies \frac{du}{dx}=2x \iff du=2xdx\\ \int 2\sqrt{ u } \, \mathrm{d}u =2\int u^{\frac{1}{2}} \, \mathrm{d}u =2\frac{2}{3}u^{\frac{3}{2}}+C=\frac{4}{3}(x^2+2)^{\frac{3}{2}}+C'=\frac{4}{3}(x^{2}+2) \sqrt{ x^{2}+2 } + C' \end{aligned} \]