The Mass Paradox

The increasing mass in a moving frame of reference gives birth to another paradox. If there are $n \ge $\textit{ 2} simultaneous observers, each one moving with a different speed $v_{1}, v_{2}$\textit{, \textellipsis ,} and respectively $v_{n}_{\, }$with respect to a body, then the mass of the body has simultaneously $n$ different values, $M(v_{1}), M(v_{2}$\textit{), \textellipsis , M(v}$_{n})$ respectively in the previous formula, which is impossible in practice, alike in the paradoxism movement.