5.5 The Substitution Rule/67

$\int _{e}^{e^{4}}{\frac {dx}{x{\sqrt {lnx}}}}$ = $\int _{1}^{4}{\frac {1}{u}}du$ = Failed to parse (syntax error): {\displaystyle \int_{1}^{4}u^\{frac{-1}{2}}du}