Application Of Derivatives

Let \(f: \rightarrow \mathbb{R} \rightarrow(0, \infty)\) be strictly increasing function such that \(\lim _\limits{x \rightarrow \infty} \frac{f(7 x)}{f(x)}=1\). Then, the value of \(\lim _\limits{x \rightarrow \infty}\left[\frac{f(5 x)}{f(x)}-1\right]\) is equal to