Integrand size = 18, antiderivative size = 63 \[ \int e^{-b^2 x^2} x^2 \text {erfc}(b x) \, dx=\frac {e^{-2 b^2 x^2}}{4 b^3 \sqrt {\pi }}-\frac {e^{-b^2 x^2} x \text {erfc}(b x)}{2 b^2}-\frac {\sqrt {\pi } \text {erfc}(b x)^2}{8 b^3} \]
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Time = 0.04 (sec) , antiderivative size = 63, normalized size of antiderivative = 1.00, number of steps used = 4, number of rules used = 4, \(\frac {\text {number of rules}}{\text {integrand size}}\) = 0.222, Rules used = {6521, 6509, 30, 2240} \[ \int e^{-b^2 x^2} x^2 \text {erfc}(b x) \, dx=-\frac {\sqrt {\pi } \text {erfc}(b x)^2}{8 b^3}-\frac {x e^{-b^2 x^2} \text {erfc}(b x)}{2 b^2}+\frac {e^{-2 b^2 x^2}}{4 \sqrt {\pi } b^3} \]
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Rule 30
Rule 2240
Rule 6509
Rule 6521
Rubi steps \begin{align*} \text {integral}& = -\frac {e^{-b^2 x^2} x \text {erfc}(b x)}{2 b^2}+\frac {\int e^{-b^2 x^2} \text {erfc}(b x) \, dx}{2 b^2}-\frac {\int e^{-2 b^2 x^2} x \, dx}{b \sqrt {\pi }} \\ & = \frac {e^{-2 b^2 x^2}}{4 b^3 \sqrt {\pi }}-\frac {e^{-b^2 x^2} x \text {erfc}(b x)}{2 b^2}-\frac {\sqrt {\pi } \text {Subst}(\int x \, dx,x,\text {erfc}(b x))}{4 b^3} \\ & = \frac {e^{-2 b^2 x^2}}{4 b^3 \sqrt {\pi }}-\frac {e^{-b^2 x^2} x \text {erfc}(b x)}{2 b^2}-\frac {\sqrt {\pi } \text {erfc}(b x)^2}{8 b^3} \\ \end{align*}
Time = 0.09 (sec) , antiderivative size = 79, normalized size of antiderivative = 1.25 \[ \int e^{-b^2 x^2} x^2 \text {erfc}(b x) \, dx=\frac {2 e^{-2 b^2 x^2} \left (\frac {1}{\sqrt {\pi }}-2 b e^{b^2 x^2} x\right )+\left (2 \sqrt {\pi }+4 b e^{-b^2 x^2} x\right ) \text {erf}(b x)-\sqrt {\pi } \text {erf}(b x)^2}{8 b^3} \]
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\[\int x^{2} \operatorname {erfc}\left (b x \right ) {\mathrm e}^{-b^{2} x^{2}}d x\]
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none
Time = 0.25 (sec) , antiderivative size = 66, normalized size of antiderivative = 1.05 \[ \int e^{-b^2 x^2} x^2 \text {erfc}(b x) \, dx=\frac {4 \, {\left (\pi b x \operatorname {erf}\left (b x\right ) - \pi b x\right )} e^{\left (-b^{2} x^{2}\right )} - \sqrt {\pi } {\left (\pi \operatorname {erf}\left (b x\right )^{2} - 2 \, \pi \operatorname {erf}\left (b x\right ) - 2 \, e^{\left (-2 \, b^{2} x^{2}\right )}\right )}}{8 \, \pi b^{3}} \]
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Time = 1.32 (sec) , antiderivative size = 63, normalized size of antiderivative = 1.00 \[ \int e^{-b^2 x^2} x^2 \text {erfc}(b x) \, dx=\begin {cases} - \frac {x e^{- b^{2} x^{2}} \operatorname {erfc}{\left (b x \right )}}{2 b^{2}} - \frac {\sqrt {\pi } \operatorname {erfc}^{2}{\left (b x \right )}}{8 b^{3}} + \frac {e^{- 2 b^{2} x^{2}}}{4 \sqrt {\pi } b^{3}} & \text {for}\: b \neq 0 \\\frac {x^{3}}{3} & \text {otherwise} \end {cases} \]
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\[ \int e^{-b^2 x^2} x^2 \text {erfc}(b x) \, dx=\int { x^{2} \operatorname {erfc}\left (b x\right ) e^{\left (-b^{2} x^{2}\right )} \,d x } \]
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\[ \int e^{-b^2 x^2} x^2 \text {erfc}(b x) \, dx=\int { x^{2} \operatorname {erfc}\left (b x\right ) e^{\left (-b^{2} x^{2}\right )} \,d x } \]
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Time = 4.97 (sec) , antiderivative size = 49, normalized size of antiderivative = 0.78 \[ \int e^{-b^2 x^2} x^2 \text {erfc}(b x) \, dx=\frac {2\,{\mathrm {e}}^{-2\,b^2\,x^2}-\pi \,{\mathrm {erfc}\left (b\,x\right )}^2}{8\,b^3\,\sqrt {\pi }}-\frac {x\,{\mathrm {e}}^{-b^2\,x^2}\,\mathrm {erfc}\left (b\,x\right )}{2\,b^2} \]
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