Integrand size = 8, antiderivative size = 71 \[ \int x^3 \text {erfc}(b x) \, dx=-\frac {3 e^{-b^2 x^2} x}{8 b^3 \sqrt {\pi }}-\frac {e^{-b^2 x^2} x^3}{4 b \sqrt {\pi }}+\frac {3 \text {erf}(b x)}{16 b^4}+\frac {1}{4} x^4 \text {erfc}(b x) \]
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Time = 0.04 (sec) , antiderivative size = 71, normalized size of antiderivative = 1.00, number of steps used = 4, number of rules used = 3, \(\frac {\text {number of rules}}{\text {integrand size}}\) = 0.375, Rules used = {6497, 2243, 2236} \[ \int x^3 \text {erfc}(b x) \, dx=\frac {3 \text {erf}(b x)}{16 b^4}-\frac {x^3 e^{-b^2 x^2}}{4 \sqrt {\pi } b}-\frac {3 x e^{-b^2 x^2}}{8 \sqrt {\pi } b^3}+\frac {1}{4} x^4 \text {erfc}(b x) \]
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Rule 2236
Rule 2243
Rule 6497
Rubi steps \begin{align*} \text {integral}& = \frac {1}{4} x^4 \text {erfc}(b x)+\frac {b \int e^{-b^2 x^2} x^4 \, dx}{2 \sqrt {\pi }} \\ & = -\frac {e^{-b^2 x^2} x^3}{4 b \sqrt {\pi }}+\frac {1}{4} x^4 \text {erfc}(b x)+\frac {3 \int e^{-b^2 x^2} x^2 \, dx}{4 b \sqrt {\pi }} \\ & = -\frac {3 e^{-b^2 x^2} x}{8 b^3 \sqrt {\pi }}-\frac {e^{-b^2 x^2} x^3}{4 b \sqrt {\pi }}+\frac {1}{4} x^4 \text {erfc}(b x)+\frac {3 \int e^{-b^2 x^2} \, dx}{8 b^3 \sqrt {\pi }} \\ & = -\frac {3 e^{-b^2 x^2} x}{8 b^3 \sqrt {\pi }}-\frac {e^{-b^2 x^2} x^3}{4 b \sqrt {\pi }}+\frac {3 \text {erf}(b x)}{16 b^4}+\frac {1}{4} x^4 \text {erfc}(b x) \\ \end{align*}
Time = 0.04 (sec) , antiderivative size = 54, normalized size of antiderivative = 0.76 \[ \int x^3 \text {erfc}(b x) \, dx=\frac {1}{16} \left (-\frac {2 e^{-b^2 x^2} x \left (3+2 b^2 x^2\right )}{b^3 \sqrt {\pi }}+\frac {3 \text {erf}(b x)}{b^4}+4 x^4 \text {erfc}(b x)\right ) \]
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Time = 0.16 (sec) , antiderivative size = 64, normalized size of antiderivative = 0.90
method | result | size |
parallelrisch | \(\frac {4 \,\operatorname {erfc}\left (b x \right ) x^{4} \sqrt {\pi }\, b^{4}-4 x^{3} {\mathrm e}^{-b^{2} x^{2}} b^{3}-6 \,{\mathrm e}^{-b^{2} x^{2}} b x -3 \,\operatorname {erfc}\left (b x \right ) \sqrt {\pi }}{16 \sqrt {\pi }\, b^{4}}\) | \(64\) |
derivativedivides | \(\frac {\frac {b^{4} x^{4} \operatorname {erfc}\left (b x \right )}{4}+\frac {-\frac {x^{3} {\mathrm e}^{-b^{2} x^{2}} b^{3}}{2}-\frac {3 \,{\mathrm e}^{-b^{2} x^{2}} b x}{4}+\frac {3 \,\operatorname {erf}\left (b x \right ) \sqrt {\pi }}{8}}{2 \sqrt {\pi }}}{b^{4}}\) | \(65\) |
default | \(\frac {\frac {b^{4} x^{4} \operatorname {erfc}\left (b x \right )}{4}+\frac {-\frac {x^{3} {\mathrm e}^{-b^{2} x^{2}} b^{3}}{2}-\frac {3 \,{\mathrm e}^{-b^{2} x^{2}} b x}{4}+\frac {3 \,\operatorname {erf}\left (b x \right ) \sqrt {\pi }}{8}}{2 \sqrt {\pi }}}{b^{4}}\) | \(65\) |
parts | \(\frac {x^{4} \operatorname {erfc}\left (b x \right )}{4}+\frac {b \left (-\frac {x^{3} {\mathrm e}^{-b^{2} x^{2}}}{2 b^{2}}+\frac {-\frac {3 x \,{\mathrm e}^{-b^{2} x^{2}}}{4 b^{2}}+\frac {3 \sqrt {\pi }\, \operatorname {erf}\left (b x \right )}{8 b^{3}}}{b^{2}}\right )}{2 \sqrt {\pi }}\) | \(68\) |
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Time = 0.26 (sec) , antiderivative size = 63, normalized size of antiderivative = 0.89 \[ \int x^3 \text {erfc}(b x) \, dx=\frac {4 \, \pi b^{4} x^{4} - 2 \, \sqrt {\pi } {\left (2 \, b^{3} x^{3} + 3 \, b x\right )} e^{\left (-b^{2} x^{2}\right )} + {\left (3 \, \pi - 4 \, \pi b^{4} x^{4}\right )} \operatorname {erf}\left (b x\right )}{16 \, \pi b^{4}} \]
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Time = 0.23 (sec) , antiderivative size = 68, normalized size of antiderivative = 0.96 \[ \int x^3 \text {erfc}(b x) \, dx=\begin {cases} \frac {x^{4} \operatorname {erfc}{\left (b x \right )}}{4} - \frac {x^{3} e^{- b^{2} x^{2}}}{4 \sqrt {\pi } b} - \frac {3 x e^{- b^{2} x^{2}}}{8 \sqrt {\pi } b^{3}} - \frac {3 \operatorname {erfc}{\left (b x \right )}}{16 b^{4}} & \text {for}\: b \neq 0 \\\frac {x^{4}}{4} & \text {otherwise} \end {cases} \]
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Time = 0.21 (sec) , antiderivative size = 55, normalized size of antiderivative = 0.77 \[ \int x^3 \text {erfc}(b x) \, dx=\frac {1}{4} \, x^{4} \operatorname {erfc}\left (b x\right ) - \frac {b {\left (\frac {2 \, {\left (2 \, b^{2} x^{3} + 3 \, x\right )} e^{\left (-b^{2} x^{2}\right )}}{b^{4}} - \frac {3 \, \sqrt {\pi } \operatorname {erf}\left (b x\right )}{b^{5}}\right )}}{16 \, \sqrt {\pi }} \]
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Time = 0.28 (sec) , antiderivative size = 61, normalized size of antiderivative = 0.86 \[ \int x^3 \text {erfc}(b x) \, dx=-\frac {1}{4} \, x^{4} \operatorname {erf}\left (b x\right ) + \frac {1}{4} \, x^{4} - \frac {b {\left (\frac {2 \, {\left (2 \, b^{2} x^{3} + 3 \, x\right )} e^{\left (-b^{2} x^{2}\right )}}{b^{4}} + \frac {3 \, \sqrt {\pi } \operatorname {erf}\left (-b x\right )}{b^{5}}\right )}}{16 \, \sqrt {\pi }} \]
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Time = 4.88 (sec) , antiderivative size = 58, normalized size of antiderivative = 0.82 \[ \int x^3 \text {erfc}(b x) \, dx=\frac {x^4\,\mathrm {erfc}\left (b\,x\right )}{4}-\frac {\frac {3\,\mathrm {erfc}\left (b\,x\right )}{16}+\frac {b^3\,x^3\,{\mathrm {e}}^{-b^2\,x^2}}{4\,\sqrt {\pi }}+\frac {3\,b\,x\,{\mathrm {e}}^{-b^2\,x^2}}{8\,\sqrt {\pi }}}{b^4} \]
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