integral of (r^3)/(sqrt(4+r^2))

Lösung

\int \frac{r ^{3}}{4 + r ^{2}} d r

\frac{1}{3} (4 + r^{2})^{\frac{3}{2}} - 4 4 + r^{2} + C

Schritte zur Lösung

\int \frac{r ^{3}}{4 + r ^{2}} d r

Wende U-Substitution an

= \int u^{2} - 4 d u

Wende die Summenregel an:

\int f (x) \pm g (x) d x = \int f (x) d x \pm \int g (x) d x

= \int u^{2} d u - \int 4 d u

\int u^{2} d u = \frac{u ^{3}}{3}

\int 4 d u = 4 u

= \frac{u ^{3}}{3} - 4 u

Setze in

u = 4 + r^{2}

ein

= \frac{( 4 + r ^{2} ) ^{3}}{3} - 4 4 + r^{2}

Vereinfache

\frac{( 4 + r ^{2} ) ^{3}}{3} - 4 4 + r^{2} : \frac{1}{3} (4 + r^{2})^{\frac{3}{2}} - 4 4 + r^{2}

= \frac{1}{3} (4 + r^{2})^{\frac{3}{2}} - 4 4 + r^{2}

Füge eine Konstante zur Lösung hinzu

= \frac{1}{3} (4 + r^{2})^{\frac{3}{2}} - 4 4 + r^{2} + C

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