At constant temperature, the equilibrium constant $\left({\mathrm{K}}_{\mathrm{p}}\right)$ for the decomposition reaction ${\mathrm{N}}_2{\mathrm{O}}_4\rightleftharpoons 2{\mathrm{NO}}_2$ is expressed by, 

${\mathrm{K}}_{\mathrm{p}}=\frac{\left(4{\mathrm{x}}^2\mathrm{P}\right)}{\left(1-{\mathrm{x}}^2\right)}$ where, P=pressure, x=extent of decomposition. Which of the following statements is true?