For the tension performance equation P C R = σ / ρ {\displaystyle P_{CR}=\sigma /\rho } , the first step is to take the log of both sides. The resulting equation can be rearranged to give log ⁡ ( σ ) = log ⁡ ( ρ ) + log ⁡ ( P C R ) {\displaystyle \log(\sigma )=\log(\rho )+\log(P_{CR})} . Note that this follows the format of y = x + b {\displaystyle y=x+b} , making it linear on a log-log graph.