1. The problem statement, all variables and given/known data The electron is traveling at a speed of β=.9999999, γ=1957, with mass mc^2=.51099 MeV. The Proton is traveling at a speed of β=.9, γ=2.29, with mass mc^2=938.27 MeV. They are heading in opposite directions, directly towards each other on the x-axis Find the reference frame where their momenta are equivalent, and find the total energy in the frame, and the total kinetic energy. 2. Relevant equations see below 3. The attempt at a solution I'm not exactly sure if I'm going about this right but I have started a lorentz transform with the momentum 4-vectors of both the electron and proton. Then I took the second component of the resultant vectors which would be equal to γp, then I set them equal to each other and tried to solve for a velocity. Am I going about his right? All the work is shown in the attached jpeg.