\[ \int \frac {\left (a x+b x^3\right )^{3/2}}{x^7} \, dx \]
Optimal antiderivative \[ -\frac {2 \left (b \,x^{3}+a x \right )^{\frac {3}{2}}}{9 x^{6}}+\frac {8 b^{\frac {5}{2}} x \left (b \,x^{2}+a \right )}{15 a \left (\sqrt {a}+x \sqrt {b}\right ) \sqrt {b \,x^{3}+a x}}-\frac {4 b \sqrt {b \,x^{3}+a x}}{15 x^{3}}-\frac {8 b^{2} \sqrt {b \,x^{3}+a x}}{15 a x}-\frac {8 b^{\frac {9}{4}} \sqrt {\frac {\cos \left (4 \arctan \left (\frac {b^{\frac {1}{4}} \sqrt {x}}{a^{\frac {1}{4}}}\right )\right )}{2}+\frac {1}{2}}\, \EllipticE \left (\sin \left (2 \arctan \left (\frac {b^{\frac {1}{4}} \sqrt {x}}{a^{\frac {1}{4}}}\right )\right ), \frac {\sqrt {2}}{2}\right ) \left (\sqrt {a}+x \sqrt {b}\right ) \sqrt {x}\, \sqrt {\frac {b \,x^{2}+a}{\left (\sqrt {a}+x \sqrt {b}\right )^{2}}}}{15 \cos \left (2 \arctan \left (\frac {b^{\frac {1}{4}} \sqrt {x}}{a^{\frac {1}{4}}}\right )\right ) a^{\frac {3}{4}} \sqrt {b \,x^{3}+a x}}+\frac {4 b^{\frac {9}{4}} \sqrt {\frac {\cos \left (4 \arctan \left (\frac {b^{\frac {1}{4}} \sqrt {x}}{a^{\frac {1}{4}}}\right )\right )}{2}+\frac {1}{2}}\, \EllipticF \left (\sin \left (2 \arctan \left (\frac {b^{\frac {1}{4}} \sqrt {x}}{a^{\frac {1}{4}}}\right )\right ), \frac {\sqrt {2}}{2}\right ) \left (\sqrt {a}+x \sqrt {b}\right ) \sqrt {x}\, \sqrt {\frac {b \,x^{2}+a}{\left (\sqrt {a}+x \sqrt {b}\right )^{2}}}}{15 \cos \left (2 \arctan \left (\frac {b^{\frac {1}{4}} \sqrt {x}}{a^{\frac {1}{4}}}\right )\right ) a^{\frac {3}{4}} \sqrt {b \,x^{3}+a x}} \]
command
integrate((b*x^3+a*x)^(3/2)/x^7,x, algorithm="fricas")
Fricas 1.3.8 (sbcl 2.2.11.debian) via sagemath 9.6 output
\[ -\frac {2 \, {\left (12 \, b^{\frac {5}{2}} x^{5} {\rm weierstrassZeta}\left (-\frac {4 \, a}{b}, 0, {\rm weierstrassPInverse}\left (-\frac {4 \, a}{b}, 0, x\right )\right ) + {\left (12 \, b^{2} x^{4} + 11 \, a b x^{2} + 5 \, a^{2}\right )} \sqrt {b x^{3} + a x}\right )}}{45 \, a x^{5}} \]
Fricas 1.3.7 via sagemath 9.3 output
\[ {\rm integral}\left (\frac {\sqrt {b x^{3} + a x} {\left (b x^{2} + a\right )}}{x^{6}}, x\right ) \]