Integraal van $$$\sqrt{x} \ln\left(x\right)$$$

Bepaal $$$\int \sqrt{x} \ln\left(x\right)\, dx$$$.

Voor de integraal $$$\int{\sqrt{x} \ln{\left(x \right)} d x}$$$, gebruik partiële integratie $$$\int \operatorname{u} \operatorname{dv} = \operatorname{u}\operatorname{v} - \int \operatorname{v} \operatorname{du}$$$.

Zij $$$\operatorname{u}=\ln{\left(x \right)}$$$ en $$$\operatorname{dv}=\sqrt{x} dx$$$.

Dan $$$\operatorname{du}=\left(\ln{\left(x \right)}\right)^{\prime }dx=\frac{dx}{x}$$$ (de stappen zijn te zien ») en $$$\operatorname{v}=\int{\sqrt{x} d x}=\frac{2 x^{\frac{3}{2}}}{3}$$$ (de stappen zijn te zien »).

Dus,

$${\color{red}{\int{\sqrt{x} \ln{\left(x \right)} d x}}}={\color{red}{\left(\ln{\left(x \right)} \cdot \frac{2 x^{\frac{3}{2}}}{3}-\int{\frac{2 x^{\frac{3}{2}}}{3} \cdot \frac{1}{x} d x}\right)}}={\color{red}{\left(\frac{2 x^{\frac{3}{2}} \ln{\left(x \right)}}{3} - \int{\frac{2 \sqrt{x}}{3} d x}\right)}}$$

Pas de constante-veelvoudregel $$$\int c f{\left(x \right)}\, dx = c \int f{\left(x \right)}\, dx$$$ toe met $$$c=\frac{2}{3}$$$ en $$$f{\left(x \right)} = \sqrt{x}$$$:

$$\frac{2 x^{\frac{3}{2}} \ln{\left(x \right)}}{3} - {\color{red}{\int{\frac{2 \sqrt{x}}{3} d x}}} = \frac{2 x^{\frac{3}{2}} \ln{\left(x \right)}}{3} - {\color{red}{\left(\frac{2 \int{\sqrt{x} d x}}{3}\right)}}$$

Pas de machtsregel $$$\int x^{n}\, dx = \frac{x^{n + 1}}{n + 1}$$$ $$$\left(n \neq -1 \right)$$$ toe met $$$n=\frac{1}{2}$$$:

$$\frac{2 x^{\frac{3}{2}} \ln{\left(x \right)}}{3} - \frac{2 {\color{red}{\int{\sqrt{x} d x}}}}{3}=\frac{2 x^{\frac{3}{2}} \ln{\left(x \right)}}{3} - \frac{2 {\color{red}{\int{x^{\frac{1}{2}} d x}}}}{3}=\frac{2 x^{\frac{3}{2}} \ln{\left(x \right)}}{3} - \frac{2 {\color{red}{\frac{x^{\frac{1}{2} + 1}}{\frac{1}{2} + 1}}}}{3}=\frac{2 x^{\frac{3}{2}} \ln{\left(x \right)}}{3} - \frac{2 {\color{red}{\left(\frac{2 x^{\frac{3}{2}}}{3}\right)}}}{3}$$

Dus,

$$\int{\sqrt{x} \ln{\left(x \right)} d x} = \frac{2 x^{\frac{3}{2}} \ln{\left(x \right)}}{3} - \frac{4 x^{\frac{3}{2}}}{9}$$

Vereenvoudig:

$$\int{\sqrt{x} \ln{\left(x \right)} d x} = \frac{2 x^{\frac{3}{2}} \left(3 \ln{\left(x \right)} - 2\right)}{9}$$

Voeg de integratieconstante toe:

$$\int{\sqrt{x} \ln{\left(x \right)} d x} = \frac{2 x^{\frac{3}{2}} \left(3 \ln{\left(x \right)} - 2\right)}{9}+C$$

$$$\int \sqrt{x} \ln\left(x\right)\, dx = \frac{2 x^{\frac{3}{2}} \left(3 \ln\left(x\right) - 2\right)}{9} + C$$$A