Our limited knowledge of the energy dependence of electron precipitation associated with auroral kilometric radiation (AKR) production is improved with the use of bremsstrahlung x-ray measurements. Simultaneous observations of bremsstrahlung x-rays above 2 keV from the Polar Ionospheric X-ray Imaging Experiment (PIXIE) on the POLAR satellite are compared with the frequency distributions of AKR waves measured with the Plasma Wave Instrument (PWI) on the GEOTAIL satellite. Various AKR characteristics such as the low- and high- frequency cutoffs and the frequencies at peak intensity are compared with various x-ray parameters such as the magnetic local times of emission, the total intensities, and the spectral shapes. In particular, it is found that higher fluxes of x-rays occur when the various cutoffs are at lower frequency. Also, higher AKR cutoff frequencies are associated with higher e-folding x-ray energy spectra.