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受欢迎的微积分 >

integral of ((x^3))/((x^2+4)^{(1/2))}

解答

\int \frac{( x ^{3} )}{( x ^{2} + 4 ) ^{(\frac{1}{2})}} d x

解答

\frac{1}{3} (x^{2} - 8) (x^{2} + 4)^{\frac{1}{2}} + C

求解步骤

\int \frac{x ^{3}}{( x ^{2} + 4 ) ^{\frac{1}{2}}} d x

使用指数法则:

\frac{1}{a ^{b}} = a^{- b}

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

= \int x^{3} (x^{2} + 4)^{- \frac{1}{2}} d x

使用换元积分法

= \int \frac{u ^{\frac{1}{3}}}{3 ( u ^{\frac{2}{3}} + 4 ) ^{\frac{1}{2}}} d u

提出常数:

\int a \cdot f (x) d x = a \cdot \int f (x) d x

= \frac{1}{3} \cdot \int \frac{u ^{\frac{1}{3}}}{( u ^{\frac{2}{3}} + 4 ) ^{\frac{1}{2}}} d u

使用换元积分法

= \frac{1}{3} \cdot \int \frac{3 ( v - 4 )}{2 v ^{\frac{1}{2}}} d v

提出常数:

\int a \cdot f (x) d x = a \cdot \int f (x) d x

= \frac{1}{3} \cdot \frac{3}{2} \cdot \int \frac{v - 4}{v ^{\frac{1}{2}}} d v

乘开

\frac{v - 4}{v ^{\frac{1}{2}}} : v^{\frac{1}{2}} - \frac{4}{v ^{\frac{1}{2}}}

= \frac{1}{3} \cdot \frac{3}{2} \cdot \int v^{\frac{1}{2}} - \frac{4}{v ^{\frac{1}{2}}} d v

使用积分加法定则:

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

= \frac{1}{3} \cdot \frac{3}{2} (\int v^{\frac{1}{2}} d v - \int \frac{4}{v ^{\frac{1}{2}}} d v)

\int v^{\frac{1}{2}} d v = \frac{2}{3} v^{\frac{3}{2}}

\int \frac{4}{v ^{\frac{1}{2}}} d v = 8 v^{\frac{1}{2}}

= \frac{1}{3} \cdot \frac{3}{2} (\frac{2}{3} v^{\frac{3}{2}} - 8 v^{\frac{1}{2}})

代回

= \frac{1}{3} \cdot \frac{3}{2} (\frac{2}{3} ((x^{3})^{\frac{2}{3}} + 4)^{\frac{3}{2}} - 8 ((x^{3})^{\frac{2}{3}} + 4)^{\frac{1}{2}})

化简

\frac{1}{3} \cdot \frac{3}{2} (\frac{2}{3} ((x^{3})^{\frac{2}{3}} + 4)^{\frac{3}{2}} - 8 ((x^{3})^{\frac{2}{3}} + 4)^{\frac{1}{2}}) : \frac{1}{3} (x^{2} - 8) (x^{2} + 4)^{\frac{1}{2}}

= \frac{1}{3} (x^{2} - 8) (x^{2} + 4)^{\frac{1}{2}}

解答补常数

= \frac{1}{3} (x^{2} - 8) (x^{2} + 4)^{\frac{1}{2}} + C

作图

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