\[ \int \cosh ^{\frac {3}{2}}(a+b x) \, dx \]
Optimal antiderivative \[ -\frac {2 i \sqrt {\frac {\cosh \left (b x +a \right )}{2}+\frac {1}{2}}\, \EllipticF \left (i \sinh \left (\frac {a}{2}+\frac {b x}{2}\right ), \sqrt {2}\right )}{3 \cosh \left (\frac {a}{2}+\frac {b x}{2}\right ) b}+\frac {2 \sinh \left (b x +a \right ) \left (\sqrt {\cosh }\left (b x +a \right )\right )}{3 b} \]
command
integrate(cosh(b*x+a)^(3/2),x, algorithm="fricas")
Fricas 1.3.8 (sbcl 2.2.11.debian) via sagemath 9.6 output
\[ \frac {2 \, {\left (\sqrt {2} \cosh \left (b x + a\right ) + \sqrt {2} \sinh \left (b x + a\right )\right )} {\rm weierstrassPInverse}\left (-4, 0, \cosh \left (b x + a\right ) + \sinh \left (b x + a\right )\right ) + {\left (\cosh \left (b x + a\right )^{2} + 2 \, \cosh \left (b x + a\right ) \sinh \left (b x + a\right ) + \sinh \left (b x + a\right )^{2} - 1\right )} \sqrt {\cosh \left (b x + a\right )}}{3 \, {\left (b \cosh \left (b x + a\right ) + b \sinh \left (b x + a\right )\right )}} \]
Fricas 1.3.7 via sagemath 9.3 output
\[ {\rm integral}\left (\cosh \left (b x + a\right )^{\frac {3}{2}}, x\right ) \]