The proper factor by which the video should be sped up is closer to 2.47X. Basically what it comes down to is the square root of the factor by which the acceleration is greater/lesser. For the moon, gravity is 1/6th that of Earth's, so if the footage was filmed in Earth gravity, you would need to play that back at √1/6 or 40.8% speed to be consistent with lunar gravity. If you want to go the other direction, since Earth's gravity is 6 times stronger, you'd speed up lunar footage by a factor of √6 (or 2.47X) to be consistent with Earth gravity.
There is no "mathematical formula" that I know of that definitively "proves" that the footage could not have been slowed down, but fortunately, math is not required. Just speed up the footage the proper amount (2.47X) and then watch EVERYTHING. What these hoaxers fail to realize is that the ONLY thing that changes is the downward acceleration of gravity. Any other motion should be unchanged. When you speed up the footage to what hoaxers will say is the "original recording speed", all motion that gravity is not responsible for looks way too fast, jerky and unnatural. Any hoaxers who view this footage and claim it looks natural are simply lying to themselves, and if they refuse to acknowledge this, then there isn't anything that will convince them anyway; certainly no math will.