Senior Kangaroo 2021 Q19

The function $f\left(x\right)$ is defined as $f\left(x\right)=\frac{x-1}{x+1}$.

The equation$f\left(x^2\right)\times f\left(x\right)=0.72$ has two solutions $a$ and $b$, where $a>b$.

What is the value of $19a+7b$?