Integrand size = 18, antiderivative size = 108 \[ \int \frac {e^{-b^2 x^2} \text {erfc}(b x)}{x^4} \, dx=\frac {b e^{-2 b^2 x^2}}{3 \sqrt {\pi } x^2}-\frac {e^{-b^2 x^2} \text {erfc}(b x)}{3 x^3}+\frac {2 b^2 e^{-b^2 x^2} \text {erfc}(b x)}{3 x}-\frac {1}{3} b^3 \sqrt {\pi } \text {erfc}(b x)^2+\frac {4 b^3 \operatorname {ExpIntegralEi}\left (-2 b^2 x^2\right )}{3 \sqrt {\pi }} \]
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Time = 0.10 (sec) , antiderivative size = 108, normalized size of antiderivative = 1.00, number of steps used = 7, number of rules used = 5, \(\frac {\text {number of rules}}{\text {integrand size}}\) = 0.278, Rules used = {6527, 6509, 30, 2241, 2245} \[ \int \frac {e^{-b^2 x^2} \text {erfc}(b x)}{x^4} \, dx=-\frac {1}{3} \sqrt {\pi } b^3 \text {erfc}(b x)^2+\frac {2 b^2 e^{-b^2 x^2} \text {erfc}(b x)}{3 x}-\frac {e^{-b^2 x^2} \text {erfc}(b x)}{3 x^3}+\frac {b e^{-2 b^2 x^2}}{3 \sqrt {\pi } x^2}+\frac {4 b^3 \operatorname {ExpIntegralEi}\left (-2 b^2 x^2\right )}{3 \sqrt {\pi }} \]
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Rule 30
Rule 2241
Rule 2245
Rule 6509
Rule 6527
Rubi steps \begin{align*} \text {integral}& = -\frac {e^{-b^2 x^2} \text {erfc}(b x)}{3 x^3}-\frac {1}{3} \left (2 b^2\right ) \int \frac {e^{-b^2 x^2} \text {erfc}(b x)}{x^2} \, dx-\frac {(2 b) \int \frac {e^{-2 b^2 x^2}}{x^3} \, dx}{3 \sqrt {\pi }} \\ & = \frac {b e^{-2 b^2 x^2}}{3 \sqrt {\pi } x^2}-\frac {e^{-b^2 x^2} \text {erfc}(b x)}{3 x^3}+\frac {2 b^2 e^{-b^2 x^2} \text {erfc}(b x)}{3 x}+\frac {1}{3} \left (4 b^4\right ) \int e^{-b^2 x^2} \text {erfc}(b x) \, dx+2 \frac {\left (4 b^3\right ) \int \frac {e^{-2 b^2 x^2}}{x} \, dx}{3 \sqrt {\pi }} \\ & = \frac {b e^{-2 b^2 x^2}}{3 \sqrt {\pi } x^2}-\frac {e^{-b^2 x^2} \text {erfc}(b x)}{3 x^3}+\frac {2 b^2 e^{-b^2 x^2} \text {erfc}(b x)}{3 x}+\frac {4 b^3 \operatorname {ExpIntegralEi}\left (-2 b^2 x^2\right )}{3 \sqrt {\pi }}-\frac {1}{3} \left (2 b^3 \sqrt {\pi }\right ) \text {Subst}(\int x \, dx,x,\text {erfc}(b x)) \\ & = \frac {b e^{-2 b^2 x^2}}{3 \sqrt {\pi } x^2}-\frac {e^{-b^2 x^2} \text {erfc}(b x)}{3 x^3}+\frac {2 b^2 e^{-b^2 x^2} \text {erfc}(b x)}{3 x}-\frac {1}{3} b^3 \sqrt {\pi } \text {erfc}(b x)^2+\frac {4 b^3 \operatorname {ExpIntegralEi}\left (-2 b^2 x^2\right )}{3 \sqrt {\pi }} \\ \end{align*}
Time = 0.05 (sec) , antiderivative size = 85, normalized size of antiderivative = 0.79 \[ \int \frac {e^{-b^2 x^2} \text {erfc}(b x)}{x^4} \, dx=\frac {1}{3} \left (\frac {e^{-b^2 x^2} \left (-1+2 b^2 x^2\right ) \text {erfc}(b x)}{x^3}-b^3 \sqrt {\pi } \text {erfc}(b x)^2+\frac {b \left (\frac {e^{-2 b^2 x^2}}{x^2}+4 b^2 \operatorname {ExpIntegralEi}\left (-2 b^2 x^2\right )\right )}{\sqrt {\pi }}\right ) \]
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\[\int \frac {\operatorname {erfc}\left (b x \right ) {\mathrm e}^{-b^{2} x^{2}}}{x^{4}}d x\]
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none
Time = 0.26 (sec) , antiderivative size = 122, normalized size of antiderivative = 1.13 \[ \int \frac {e^{-b^2 x^2} \text {erfc}(b x)}{x^4} \, dx=\frac {2 \, \pi ^{\frac {3}{2}} \sqrt {b^{2}} b^{2} x^{3} \operatorname {erf}\left (\sqrt {b^{2}} x\right ) - {\left (\pi - 2 \, \pi b^{2} x^{2} - {\left (\pi - 2 \, \pi b^{2} x^{2}\right )} \operatorname {erf}\left (b x\right )\right )} e^{\left (-b^{2} x^{2}\right )} - \sqrt {\pi } {\left (\pi b^{3} x^{3} \operatorname {erf}\left (b x\right )^{2} - 4 \, b^{3} x^{3} {\rm Ei}\left (-2 \, b^{2} x^{2}\right ) - b x e^{\left (-2 \, b^{2} x^{2}\right )}\right )}}{3 \, \pi x^{3}} \]
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\[ \int \frac {e^{-b^2 x^2} \text {erfc}(b x)}{x^4} \, dx=\int \frac {e^{- b^{2} x^{2}} \operatorname {erfc}{\left (b x \right )}}{x^{4}}\, dx \]
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\[ \int \frac {e^{-b^2 x^2} \text {erfc}(b x)}{x^4} \, dx=\int { \frac {\operatorname {erfc}\left (b x\right ) e^{\left (-b^{2} x^{2}\right )}}{x^{4}} \,d x } \]
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\[ \int \frac {e^{-b^2 x^2} \text {erfc}(b x)}{x^4} \, dx=\int { \frac {\operatorname {erfc}\left (b x\right ) e^{\left (-b^{2} x^{2}\right )}}{x^{4}} \,d x } \]
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Timed out. \[ \int \frac {e^{-b^2 x^2} \text {erfc}(b x)}{x^4} \, dx=\int \frac {{\mathrm {e}}^{-b^2\,x^2}\,\mathrm {erfc}\left (b\,x\right )}{x^4} \,d x \]
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